My dad told me my grandparents threatened to kill him

Hi Reddit! Obligatory i dont post here much lurker blah blah and stupid phone formatting, writing from work whatever.

Some background information is that i (19m) have a very close relationship with my grandparents (60-70ish m/f moms side) and mom(39f), i love them a lot as ive felt as if theyve always been there for me even despite their shortcomings and previous fuck ups. I've never been close with my dads side or my dad(44m) as my dads side was never really nice to my mom or to each other so gatherings were rare and so i never ended up knowing them as well as my moms side. My dad is a completely different story that i could write a whole different post about but to keep it short and simple, my therapists and everyone else around me (i say it like this because i am having a hard time trusting my own memory at the moment) have said to me that my dad shows signs of being a narcissist and i have been told he is really abusive. My parents split about a year or so ago now while my dad was in the hospital, as my mom said it was one of the easiest times she could get away from him. The breaking point for my mom was me and my brother telling her about our stories as we were all joking around and it slowly began to get serious. I'm getting off track but at this point you should have enough information (maybe too much LOL) to understand my relationships with everyone im going to talk about.

Recently ive been having a hard housing situation as my dads aunt passed away and we were living in her house so ive had to reach out to my dad for a lot of help and for a bit my mindset was that i cannot hold hate in my heart for him forever as he is my father. I asked for a ride around (see my mom at her work etc..) and during this ride i told a story that my coworker told me about my moms hometown, ill call my moms hometown hoto and coworker/dads lito just for quicker spelling lol.

The story was about how my coworker went up to Hoto for a party, she was younger and it was roughly the 90s and hoto/lito have SERIOUS beef like HISTORICAL beef, so when she arrived to hoto party, hoto attendees figured out she was from lito and began making fun of her. Coworker said some stuff and then mentioned how everyone at hoto then started doing hard drugs, specifically skiing (iykyk) and she left

This story was interesting to me because my mom is an ex addict, so it put into perspective for me my moms upbringing along with all the fucked up shit my moms friends and her would do. Which is what i told my dad, almost bar for bar. Then my dad brings up my grandparents and how they never put the blame on my moms past friends, to which this then turns into a tirade about my grandparents and subsequently my mom. He begins to say that he never did anything abusive and it was all to protect me, he never shit talked me behind my back, he never was abusive to my mom and it was all my mom who was abusive.

This upset me, and i ended up reminding him that i remember it and then he defended himself by saying he was always supportive of me (im trans) and he dropped the bomb that my grandparents used to talk behind my back with transphobic things and then he ALSO TOLD ME that my grandparents and mom never believed in me.

Then he tells me that the only reason they moved to Hoto when i was young is because my grandparents told him that they would "take him out" or something?? i started spacing out so i didnt catch what he said they told him specifically, but then my dad brought up how my grandparents have connections or something so he was scared and quickly agreed to move to hoto

(My dad said a LOT more but im RUNNING LOW ON SPACE HERE)

This made me even more distressed as I LOVE my grandparents, even if they are kind of hardheaded and were awful parents. And i love my mom even if there was a couple of times she wasnt the greatest mom, i know she was just stressed as the only one who consistently supported our family. My dad on the other hand, has consistently lied for sympathy (going as far as to lie about having cancer to me and my brother) and was extremely abusive to my brother and especially me. BUT what if he is telling the truth? What if I'm siding with horrible people?

So my question is am i crazy for not trusting my dad and would it be unreasonable to cut him off completely? Im open for any other questions asking for more details, i am just a little frustrated and upset by this situation because i thought my dad had grown from this behavior.