Partner of someone with depression, need advice

My partner (33NB) has been struggling with depression for nearly ten years now. When I noticed it was getting bad I encouraged them to start seeing a mental health professional, which led to them seeing both a psychiatrist and a therapist. Things were going okay until COVID, which had a pretty negative effect, but overall they were still functioning okay. One of their close friends is a user of weed, mostly edibles iirc. They went on a trip together and they tried it and noticed it helped them mentally, so after talking with their therapist they decided to start using it

I am almost certain she told them it's helpful but to take frequent breaks, I can't remember the exact term but I remember them mentioning taking breaks in between sessions. As time has gone on their use has increased exponentially, to the point where I can't remember the last time they were able to go more than an hour or two sober. They've started to self harm again, though they haven't disclosed that to me and I'm not sure if they've disclosed it to their therapist. I can hear them smacking themselves when they think I'm out of ear shot. Twice they've called me to come home when I've been out because they were afraid they'd hurt themselves if I wasn't there. Their social anxiety has gotten extreme, to the point where we can't be out of the house for more than an hour or two, less if it's in a crowded area. They maybe leave the house once every other week - or at least that's what it feels like. Their sleep schedule is non-existent, they've lost so much weight from a lack of appetite that their clothes don't fit anymore.

Back when I noticed their weed usage had increased I brought up talking to their therapist about it. I noticed their depression was on the downslide and had done some reading, both from journals and from accounts on reddit, that supported the theory that heavy usage is more likely to worsen depression over time. That conversation didn't end well, I was told they'd trust the professional. I don't know that it was ever brought up. That was maybe a year or two ago. Lately anytime their depression is triggered, they spend the rest of the day in bed asleep. Sometimes they get a bit verbally hurtful to me, and it's getting really difficult to handle. We have a good day maybe two or three times a month at this point.

Today I asked them again to bring things up with their therapist. I feel she either isn't aware of how extreme their use has gotten or they haven't looked into how heavy, constant use can affect people with depression. I came home today, and normally they have therapy every week on Wednesday. They said they haven't used it today, and I asked what the therapist said. They said they didn't have an appointment today. I asked if they had one tomorrow, and they said they had to call to get an appointment. I don't know what to do anymore. They made sure to tell me it hasn't been good for their self harm, but they'd stop if I needed it for our relationship.

They've been getting meaner, not intentionally but the words still hurt, and they were never mean before. I don't think they'd hit me, but they did put a hole in a door last year. I'm afraid to talk about things, because they immediately get defensive or shut down and leave to go sleep. They have a massive fear of police and EMTs being called, so if it ever got to the point I was forced to call them, I'm afraid it'd fracture our marriage to the point of no return.

I'm normally a levelheaded person, and I think I've spent every day this week crying over something said to me or them leaving me alone again to sleep their life away, only to get up when I need to go to bed. They haven't slept in bed with me for a few nights now, even after I insisted they come to bed. I don't know what to do. I'm afraid I'm going to come home to a body if I ask them to stop, and I'm afraid if they continue as is the same thing will happen. They won't see doctors outside of their therapist, and after today I'm concerned about if they are still showing up to sessions.

Sorry for the long rant, any advice is much appreciated.