I am so sorry you are going through this. Noone can tell you how you are supposed to act when he is drinking. But al anon can help you figure out how you feel about it and what YOU want to do about the situation you are in.
You cant help him. You cant fix it. Either he is going to decide to stop drinking or he is not. Al Anon can help you decide how you want to deal with it regardless of what he decides to do.