As far as what you say when he comes home, you really don't need to say anything unless or until he brings it up. You don't have to announce you have changed, you just start acting in accordance with your conclusions.
Detachment is good. If he comes home and is charming, say, "That's nice." If he announces his intention to go to more meetings, say, "That's good." If he starts analyzing his problem and why he's been having trouble or something like that, you can just say, "Hm, sounds like you've been giving this a lot of thought." You don't have to engage with it.
Detachment just means not involving yourself in his disease. Non-committal comments make it clear you aren't "punishing" him but rather, you are not choosing to engage in the old dance.