I know that drinking with him is not a good idea ever but if he is going to do it anyway or already is, what am I supposed to do??
What do you want to hear? When you drink with an alcoholic, you are condoning his drinking. You are telling him that you accept it. So keep your eyes open - If he can't get sober and stay sober, his alcoholism will soon progress. Instead of relapsing once a month, it will be every weekend... and then it will progress to every day...
What are you going to do if that happens? When will enough be enough? It's always good to have firm boundaries in place about the kind of behavior you accept in your life.
I understand your frustration and the thinking that nothing is black and white when it comes to alcoholics and relationships. Most of us thought that our situation was unique when we came here - that our alcoholic/addict significant other could beat it - if we stuck by them and helped them. They just needed a little support and they would get better.
But, the truth is difficult to accept. You cannot help an alcoholic get better. The best you can do is to get out of his way and give him time get better on his own. People here aren't going to lie to you about their experiences with alcoholic boyfriends, children, husbands... Drinking IS toxic to an alcoholic. and it IS toxic to the family members that surround him.
Would you advise your best friend to stay in a relationship with an active alcoholic who can't stay sober, and blows all his money on booze once he starts drinking?
I hope things work out the way you want them too, and I also hope you prepare yourself for when they don't. Just remember - you didn't cause his alcoholism, you can't control his alcoholism, and you cannot cure his alcoholism. It's not your problem to own. When he's ready to quit, he'll quit. But right now, he's on a slippery slope. And you are choosing to have a front row seat to his disaster.