Do not tell his wife. You do not have the right to do that and I’m suspecting you are doing this with hopes that she will see your side and/or alleviate your guilty feelings. You left the relationship, so move on. I don’t mean to write words that can sound harsh, but you didn’t tell the wife when you were in the relationship, so why now? I suggest a clean break from the guy and the situation and hope that you can forgive yourself (I’m not judging you at all, but based on your words, it sounds like you are suffering). I hope this helps.