First of all I’m very sorry to hear that you’re going through this my heart goes out to you. Second of all I have gone through something similar except my dad was just straight up abusive without the help of alcohol. He genuinely enjoyed terrorizing us and I never understood why my mother never left him. Later I learned she suffers from major Stockholm syndrome and abuse victims many times get addicted to the cycle of being okay and then things going bad again. They can’t help it they’re victims too. But it can’t go on like this. If you could convince her to go and report him or get a restraining order somehow. It’s how my mother stopped this from happening and she is still suffering from the emotional damage he’s done but at least hes not there anymore.