Try to talk to an Interventionist, (an Addiction's Therapist) and they can give you an idea of how to intervene on a loved ones behalf. If you can, look up the show Intervention and you'll see how that works. It's the best way to handle an addict resistant to treatment.
Let others know of the problem, ie. his folks/doctor/ (if they don't know or they don't know the extent).
Never allow a drunk to drive, call the police on them before allowing it. Help often comes by way of court ordered intervention. It might lose him a job, but it won't lose him his life (or others).
Support and be in his life only when in recovery, back away from enabling a using addict (as you're doing, thus the "becoming" ex.
Read and learn what you need to, (as you are) and never go back to enabling. (an addict will blame you for not acting sooner, once in long term recovery).
Do you have children? I HOPE YOU COME BACK.