Caregiver for mother with MS and elderly alcoholic father. Any advice?

I am the caregiver for my mom, who. Has end stage MS, and also take care of my father. I do all the cleaning, laundry, grocery shopping, cooking, as well as look after my mothers daily needs (her meds, keeping her clean, changing her catheter, etc). My father has been abusive my whole life, and this has not mellowed with time. I had the flu this weekend and had to literally hide in the tiny room that is my "space" and listen to him hurl all sorts of accusations at me (I was upstairs doing drugs, I was lazy, etc). Despite everyone in the area having this it's going around, my having it must be a fraud. He is a disgusting person when he is like this , but the flu is not the only time he hurls abuse. He has vodka hidden in the garage and when drunk, he gets very ugly, and includes hurling abuse at my mother as well. I don't even drink, but I've seen him tear apart our self esteem our whole lives. He treats my siblings who do not even visit much less help out, with nothing but kindness. If I leave, my mother will go into a nursing home, which I do not want to have happen. When I've tried to talk to my siblings, I've been told I live here rent free so if I don't like it, leave, or I am reminded that it is his house. I don't know what to do. Sure I can prove a point by leaving but the result would be to harm my mother, the innocent victim here. Any advice?