How do I tell a parent I want them out of my life?

LONG POST TW: mention of drugs, alcohol, emotional abuse

This is about my step-dad. He’s always been there for me when I need something and has been around since I was 7 (I’m 21) He’s always had a drinking problem; one of my first memories of him is him passing out at the table and asking my mother why he is sleeping there and not going to bed.

A few years ago he was diagnosed with bipolar disorder and he refuses to take his meds. Once he’s feeling better he stops taking them and ends up in that loop of party-feeling like a different person-take meds for a few days until feeling better-party.

As of the past few months we suspect he has picked up a drug habit but I don’t pry because I never see him. I had a 19 year old friend pass away from and first degree homicide related to drug issues. Last night he showed up at my friends parents house asking to be driven to the druggy part of town. They called me asking for help on what to do and I immediately felt embarrassed. I know I shouldn’t and that we have to help him get the attention needed to break the cycles he’s been in. He’s been taken to rehab many times but as soon as he’s out he’s back to what he was doing. My mother has tried everything to get him back on track because without the drinking and without the drugs he is an amazing person.

He can become violent at these times as well. He doesn’t hurt anyone but causes more damage to objects and himself. He emotionally abuses my mother and is always calling her down but she keeps going with it because she’s scared of him hurting himself.

What is really terrifying me and makes me feel so incredibly bad is that a month ago I had a chemical pregnancy. If I were to have carried to term I wouldn’t be able to take a child around there. I don’t want that life for them because that life sucks and I’ve dealt with it all my childhood. I moved out at 17 but I still feel everything that happens at the house. I can’t do it anymore. I need to get my mother out somehow as well. I don’t have any clue on what I should do or how to even say that I don’t want him in my life anymore.

I feel like I probably said some insensitive things but I don’t know how else to tell this bit. I’m sorry that this is so long but it’s mainly a rant.

If you did. Read this, thank you ❤️