Dear Corkie,
He's drinking. There is no earthly way someone can have alcohol on their breath if they haven't ingested it.
***
You know that story about the guy who hires a private investigator to find out once and for all whether his wife is having an affair? He doesn't want to believe it, but he can't help the creeping suspicion. After a week of investigating, the private eye meets with the husband and shows him the evidence he's gathered: letters between his wife and another guy, photos of his wife and the other guy out dancing, then photos of them going to a motel, then photos of the two of them through the motel window in their underwear, then a photo of the wife pulling down the shade...
"Argh," says the husband. "See what I mean? The uncertainty is killing me! If only I had PROOF!"
I like that story because who hasn't been in that position? It takes a while to face an awful truth.
But to answer your question:
if I trust my gut and walk away from this...what if I'm wrong?
Let's say--hypothetically--you walk away just as he really is around the corner from total recovery. It doesn't have to be black or white. You might leave, get busy with your own things, and then maybe in six months or a years time he'll show up, all happy and healthy and recovered, and you two can make another go of it. Stranger things have happened.
Or he won't recover and he'll just find someone else to lie to, and it won't be your problem anymore...