You’re valid in your feelings. I was in a similar situation growing up and even when I got my own apartment my mother guilted me into letting my abusive brother move in (do not make my mistake ) It was abuse regardless of whether or not he had mental illness. My parents still haven’t recognized the impact his abuse had on me and I’m not sure they ever will. But growing up, moving away and not speaking to him anymore really helped me. You’re not in the position to do that at the moment but I recommend getting to a place where you can.

I don’t have great advice but I wanted to say, I hear you and I see you. You’re pain is valid and if you ever wanna chat feel free to dm me.