You say he was a RA when you met, but you drank and smoked together. So he was not a RA, he was an A. He has never been in recovery according to the history you provided. He tells you over and over that he's stopping, but he never has. So he lies and hides.
Of course he's "on the wagon" again. He'll do whateve it takes to keep you enmeshed. That's what the disease does. You set a line in the sand with divorce papers, then you back off. He learns you can be manipulated. This is a progressive disease, it will only get worse. How many more years do you want to play the game? You didn't Cause it, can't Cure it, and can't Control it. All you can do is decide what you want for YOU.
If you're not ready to leave, you're not ready to leave. But be very careful about making threats and not following through. Say what you mean, mean what you say, don't be mean about it. Are you in AlAnon? Have you read "Codependent No More"? These would both help you sort this out for yourself.
Based on his history, I would not by his "on the wagon" story again. Actions....not words.