I believe the best way to seek help for him to seek help for yourself. Ala-non is a wonderful program and I'm sure there's meetings online if you can't or don't want to attend in person The people there have gone through what you are going through. They understand. Too much to mention here, but I strongly suggest Ala-non. They're the experts. They know the mistakes we all make in dealing with the addict. It's not your fault and actually, it's not your son's fault either. He doesn't want to be an alcoholic. It is a mental disease.
I wish you the best and your son as well.