Lunakim, it this was a really good friend of yours asking for your advice what would you do?
The 3 c's are important here. I didn't cause it, I can't control it and I can't cure it. There is nothing you can do to make him want to get better he will only do that when he is ready.
Go to some al-anon meetings, they will help.
BTW the fact that you are on a recovery forum asking for advice before the wedding is not a good omen for a long and happy marriage.
your friend,