I'm an addict. When I was high all the time, I could see everyone around me struggling with it, but I just could not help myself. I've been to rehab several times before I got really serious, and I've been sober ever since. It will go two ways, he won't get help or he will. The first step is admitting it's a problem, and it sounds like he's acknowledged that several times.
No matter what, don't feel like it's your fault at all, or that you're obligated to keep helping him. It's stressful on loved ones, and they don't deserve any of it. If you can help, and WANT to help, then do it, but don't let it risk your own personal health.
As for AA..... I quit going to NA a long time ago. It can be pretty shady, and they like to try to convert you in an attempt to keep you sober, which I think is immoral. There are plenty of other support groups, but if he's not willing, he's simply not willing, and that's a shame, really.