He has problems with drink, which he may be able to change.
However he cannot change the underlying problem which is that he is a nasty man.
You have blinkers on to his bad side, you're acting as if he is just the nice part of him. but that's not true, the "real" him is both sides.
However much you drank, would you speak to him in the way he's spoken to you? Or hit him?
The drink doesn't make him be an arsehole. He IS an arsehole.
My current, lovely DP drinks, probably more than is good for him to tell the truth, but he is never nasty to me. He got drunk last night, for example, and do you know what he did? We danced round the front room to Glastonbury on the TV. When he is drunk he gets soppy and says nice things so me. He would never say abusive things, because he is not an abusive man.
I'm sorry to say that your current partner is an abusive man, and that will not change, no matter how many times goes to the Dr. His treatment of you is absolutely inexcusable.
The best thing you can do with regards to talking to him is to find a way to stop caring about what he does or feels (easier said than done I know) and simply inform him that you've left.
I don't blame you being scared. If I was you I'd leave when he's not there and tell him you've left from a distance, on the phone, to make sure he can't hit out at you or emotionally blackmail you into staying.