I 16(m) just want to help but don't know what I can do

I have been struggling with this for a while and can't take it anymore. I have only just been diagnosed with Generalized anxiety disorder and social anxiety disorder and medicated. I don't know how to word all of this so it will probably be a lot of word vomit.

My mother has been with an emotionally abusive man for maybe 5 years now. He is awful in every way. He's bigoted which is particularly bad for me because I'm trans and gay. If I ever try to talk to my mother about it he turns it into an argument and what's worse is she usually sides with him because he'll scream at her if she doesnt. All around he's a narcissist and I don't mean that just because I hate him I genuinely think he needs help but all he gets is drugs that he sells.

The main reason I haven't done anything is because I see him as actually dangerous. This has happened before when I was very young we had to leave the stae we lived in to escape her ex. Her fiance has guns and drugs and I'm scared to provoke him. My mother tells me he wouldnt actually shoot anyone but I don't know why she hasn't broken up with him if she believes that. I mean she even told us he had a gun to her head. She says she hates him and they've even called the cops on each other and broken up before but it never sticks. I'm really scared she'll get hurt so I've tried to do things before but I'm worried she'll hate me, even typing this is making me sick like she'll find it and get mad.

I can't call the cops because they do drugs and even if I could call they probably wouldnt or couldnt do anything. My mom won't leave him and I don't know why I geg it's hard to leave abusive situations but she's been through it before and it was rough but I just wish she though it was better than staying with him. I just need advice or help I don't know what to do.