No, drinking alcohol is not ok. He's an addict, and just replacing one substance with another substance. You have every right to feel the way you do towards him, including sexually.
My ex was very unattractive when using any substance, got very angry, and was annoying more than anything. Saddest part is that her sex drive was way higher being messed up, but it turned me off and I refused much like you did. Sex to me is something that's way better naturally, not forced like addicts try to do.
I'm sorry you are going through this. You did the right thing by posting here, and have a great of people who have been in your shoes.