He says that he wants to understand WHY he drinks and uses drugs.
He drinks and uses drugs
because he is an alcoholic and a drug addict.
Nothing you say or do is going to help him until he accepts that fact and does what it takes to recover. Asking him to attend 6 Al-anon meetings isn't going to fix him either, especially if he's struggling with AA right now... It's really just another 12 step program. The steps are pretty much the same after the first one - and it sounds like that's the one he's stuck on.
Codependency, like addiction, is a cunning and baffling disease. It takes a lot of work to recover and stop trying to save people from themselves. And it isn't easy to change. It's uncomfortable at times.
But if nothing changes, nothing changes...
I think you are on the right track, when you focus on helping yourself. Your therapist has suggested you take a break from helping him. And you agreed 5 months would be an appropriate amount of time. I realize that it sounds nearly impossible right now, but maybe you can do it if you focus on it - one day at a time - like an addict has to focus on sobriety.
Are you working the steps at Alanon with a sponsor? Work the program you wish he'd work. Lead by example.
His recovery is in his own hands. It sounds like he knows what he needs to do. Whether he does it or not is up to him...