I wish I had some wonderful story to tell you. Maybe you could look on the AA part of this forum? I had a cousin who went through this. I don't know the details but that she suffered from seizures or something, swelled up and so forth and he went through a period of recovery then it happened again. And the third time she died. She was about 45. My point is that besides prayer you can only do what all the books and al-anon tell you to do. Which from my understanding is let them hit bottom. Detach etc.
I wonder if it might help to ask him to pray with you? Not sure what others think. I am not that religous but I can remember many times praying for someone who had no idea how worried I was for them. Perhaps holding his hand while he's in a hospital bed an asking to him say an outloud prayer with you.
"Completely surrender your loved one into the hands of God" — Norman Vincent Peale. "The Power of Positive Thinking" (Chapter 11-how to use faith in healing)