Ditto to everyone else. NEVER question your own gut instinct. NEVER. What if you go with it and you're wrong? TERRIFIC! It means that he's on a path to recover and, like Barb pointed out, over time he will indeed Prove It!
What if you DON'T listen to that voice and you were right all along? Then you get dragged right back in to the crazies.
I say all of this but the bottom line is that it is HIS recovery and only time will tell. We codies tend to want to over-analyze everything and try to predict the future and the fact is, its impossible to predict anyone's future. What we CAN do is try to shape our own futures by educating ourselves, learning from past events and listening to our inner voice.
Trust your gut. Always.