OP, you know you can't marry him. It would be a completely insane move. Thank God you're not married now.
My friend is 50 and her husband is 55. Wayyyy back when they were just living together, in 2003, there was an incident where he got so drunk he urinated up the wall in the living room, and didn't even remember.
They used to be a happy couple, but his problems became worse over the years - the problems the drink is masking, I suppose. They had a really bad divorce around 2015. He was a mean drunk.
Fast forward to now. He's still a drunk, so much so that he's had liver cancer and still can't stop. He's been in trouble with the police, and he doesn't see much of his kids anymore, which has been the case for years.
The moral of the story is, it's a real pity she didn't dump him after that incident all those years ago. I'm absolutely NOT blaming her. None of us have a crystal ball, and she didn't know anything about alcohol abuse and outcomes - neither did I. Or any of my circle. We couldn't look stuff up back then like you can now.
But take the lesson from her story.
And if you need any further convincing, watch Louis Theroux's excellent documentary about people living with alcohol addiction.
I know it will be hard to leave him, but you must. You are drowning in the wake of an addict, and you MUST save yourself.
Watch this. And remember that his addiction may become worse and worse if he can't beat it. And many can't. Even if he can stay away from alcohol, as one commenter on this documentary says in the comments somewhere, he's only ever one drink away from complete madness. no matter how long he's been sober. Addiction is a lifelong disease.