What do my partner (M18) and me (M18) do moving forward from here?

Okay!! So I really don't even know where to start this but I guess here I go lol (partner : transM 18, me : transM18)

My partner and I have been together for almost 2.5years, throughout these years we have gone through a lot together, we used to live with his family but it is a complete sh* show so we moved into my parents house which is just a slightly more manageable sh*t show, so we've become dependent on each other on and off throughout the relationship, and we've become each other's biggest defense/comfort but also each other's biggest tension/sadness in the same hour.(for mental health context because I feel its important, he has BPD and I am Bipolar I)

On April 14 I left my parents house and went to move onto a campus for school, it was a scary thing for the both of us but while I was there, I thrived, I felt happy for the first time in a long time, I still called him every night, visited every weekend, and I included him in everything by debriefing my days with him at night (at least I thought I did), and I discovered a lot of things about myself and genuinely felt like I found who I was. I regrettably got kicked out of that school and came back home for good August 3rd.

When I came home, he tried his hardest for a couple days to be there for me because I was grieving about losing my school, and I think this is where the snowball started rolling, but I think I didn't grieve how he expected me too and it threw him off? I didn't need someone babying my feelings and comforting me for this, or I didn't want to need that really, I cried for like a day and then sucked that shit up, accepted I couldnt do anything, and just tried moving on, pushing past like it didn't happen, joking, laughing and falling back into old habits, it probably wasn't the healthist way to get through something but I made it through how I knew how too. I think he expected me to break down? And when I didn't after a couple days, he broke down.

For I wanna say a week after I was kicked out in August it was kinda torture for me, something in him like snapped per say(?) and he started remembering a lot of repressed dark childhood trauma of his, and it shattered him, but I wasn't mentally there still because it had only been three days since I lost my everything at that point in time. Almost like once a day for 2 hours that week he would break down on me about this dark shit from his childhood and I would try to comfort him as best as I could but it wasn't ever good enough for him, then it would turn into a conversation about how much he wants to move out of state to go live with his dad because he hates my family and my house so much and he cannot ever go back to his mom's house. (Sadly his dad's isn't an option and he knows this) I'll keep trying to comfort him up until he turns and attack me for "abandoning" him with my toxic terrible family when I moved into my campus, and how I moved on without him and started a whole new life, I'd get upset seeing as how that wound was still fresh and he made me seem like a terrible person for trying to better myself, and then he'd go on and on about all the little and massive things I've done throughout the whole relationship that ever hurt him, I'd (regrettably) throw it right back at him and beg him to stop, then he'd cry on me and start asking me why I even stay with him.

It all really hit a breaking point when he locked me in my room at 3am on August 11th and started lecturing me about how I cheated on him, NOW HOLD UP BECAUSE ITS A LOT MORE COMPLICATED THAN THAT, when I was at school, I said I discovered things about myself, I found out I was poly by falling and like really falling for one of my classmates, when I found out I had these feelings I tried to figure out how to make it stop because I didn't want to cheat on my partner but these feelings were strong and reciprocated, so I ended up just admitting to myself that I might just be the type of person who falls for multiple people, I talked to my partner about it one weekend when I came home, now here I will admit I did kiss this guy a very few times the week of me coming home to tell my partner and I didn't tell him till recently, I regret that, have talked to my partner about it now and have accepted the trust loss, but moving on with the story, I told him one weekend I was poly and explained to him that I wanted to open our relationship for one specific person, he agreed but as long as me and this person we just FWB, I also agreed, we moved forward for a couple weeks okay with this agreement until I was kicked. I was sleep deprived, I was hormonal, I was not in the right mental space to be lectured at 3am about how I'm a dirty dirty whore over a situation we both agreed too so we had a long bad fight.

On August 12th me and his step brother checked him into a really sh*tty hospital nearby to try to get him transferred to the mental hospital. He wanted to go, he said he didn't feel like himself and I think this is important to note, he truly told us he would wake up some days and he wouldn't feel like he was himself anymore, like he wasn't real almost, so we all really really pushed to get him put in the psychward because that's where he said he really needed to be. Welp the cr*ppy small town local hospital said there was absolutely nothing wrong with him after sedating him over and over again throughout his stay there (he's freshly 18 as mentioned above mind you??) and then had me check him out the literal next day in the afternoon, handed me some damn managing teen stress paperwork, like gee thank this really helps with existential(?) childhood trauma.

The rest of August and the very beginning of September were alright from what I can remember, we had some fights on and off but I was blind to his decline the whole time, he was constantly doing something constantly working, not sleeping for days, and I mean like 3-4 days and then crashing for a whole 16 hours and then up again for days, drinking cup after cup of coffee, cleaning, running, parenting my siblings, training the animals, cooking, starting random projects, just always doing something and never giving himself a break unless he dropped, I was begging him majority of the time to come to bed, sit and watch a movie with me, spend just 5 mins of your day sitting down with your boyfriend but he wouldn't, and I was also being slightly ghosted by my FWB so I took it personally and just ignored it, decided that he was avoiding me on purpose so I'm not gonna keep begging for both of my lovers attention, it made me feel needy and annoying. But gosh do I regret not trying harder to make him give himself some kinda break because it was all such a clear sign of a manic state and I just ignored it because I got in my feelings.

Well, on September 3rd I came home with shr**ms and I accidentally over did it myself, and he took some as well while I was too h*gh to tell him he probably shouldn't with how he's been feeling lately. My tr*p was alright, not the best since I over did it and a couple moments there I was kinda worried for myself, but my partner sat me the whole time, and made sure I was fine, when I basically full came down, we sat down and I admitted to a lot of the things I did to him throughout our relationship and also admitted to kissing my FWB before I told him about my feelings, I apologized profusely and I promised him I would work to become a better person for him so that we don't have these problems in the future, he accepted my apologies and we went to bed that night together at the same time and holding each other for the first time in a couple weeks. The 4th-5th we literally slept ALL day, he got sick from the tr*p, I just needed to sleep it out of my system, he needed to puke it out, then we were fine, woke up at like 5am on the 6th and it got genuinely terrifying.

He started acting differently and talking differently, I literally have no way to explain it but I have A LOT of screenshots from 4-7am on the 8th of one of the absolute worst fights I've ever had with him but in those it shows that he just doesn't make sense with the things he's saying he sounds kinda crazy, nit picking on random things, his constant repeating of nonsensical "metaphors", the nastiness towards his family, him begging for MY cat that his mom forced ME to sell at 7am, just like acting really off, and he had been since we woke up after the tr*ps, he even started getting physically aggressive with me, throwing small unharmful things in my direction, manhandle me and yank me around when I would cry to try to get me to let him comfort me, and at times threaten me in very subtle ways "don't make me come over there" "ooo your so lucky I'm not my dad" ect ect, he never actually hit me but there were times I was scared he could, and he would also make me sob my eyes out to make himself feel something, he sit there and yell at me and rile me up by hot and colding me basically until I was confused and tired and distraught, and then sit there all monotone saying just enough to keep me crying while also demanding that I let him comfort me and hold me and put me back to sleep.

(If your willing to give genuine advice after reading all of this fully dm for the ss)

After the fight at 4-6am on the 8th, I went to sleep thinking he was sleeping with me, but instead he went on a walk (going off 3 days no sleep atp) and he almost crashed walking home, he asked a cop to take him to the hospital nearby again and he tried to check himself into the mental hospital, the hospital once again sedated him repeatedly overnight and then had me come check him out the next day in the afternoon, he slept all day when he got home, all throughout the night, and all day on the 10th because of how groggy he was from the drugs at the hospital, on the 10th when he woke up, I took care of him, made sure he was doing okay and then sat down and showed him his messages to people and how he had been talking and acting those couple of days, he didn't even recognize himself him those messages, and he got scared, he wanted to check himself into another hospital that same night after I told him everything he did but I honestly begged him not too, I can't handle losing him right now, I have so much going on in my own family/personal life that I can't handle being alone even if I'm with someone whose not all there.

We agreed to let me try to help him through this, let me try to be what he needs to get better, let me be what he needs, and then if it really comes down to it again he starts to decline like that again, that I need to send him to the mental hospital directly. So reddit I guess what I'm asking is how can I help him.. I really love him and I really want to be there for him so bad I wanna be what he needs but I don't know how to help him, and I know I probably can't I know this is way out of my expertise but please don't just tell me that, please someone help me find a way to help my lover become my lover again, I want him back so bad it hurts, and I see him in there still, we've had such a good past 2 days now and I've been trying so hard to keep his spirits up, but I don't know what I can do to keep him out of his head, I have physical restrictions keeping me from being active as well so I can't run around with him all day and keep him occupied, I want this relationship to work so bad, I genuinely love him so much.

MODS AND REDDITORS, I AM NOT SEEKING ANY KIND OF JUDGEMENT RESPONSES FROM THIS POST PERIOD. I HAVE ENOUGH PEOPLE PLACING THEIR JUDGEMENT ONTO MY RELATIONSHIP, I JUST WANT SOME ADVICE ON WHERE TO TO FROM HERE OR WHAT SOMEONE IN MY SHOES WOULD DO MOVING FOWARD

TLDR; My partner and I have a lot of mental health struggles and I'm looking for advice on how to help him with where he's at right now