Odds of a spouse would be honest about infidelity?

It could happen. But If you really want to be sure he's being honest with you get out of this relationship now and then it won't matter whether he is or not. The women in the street will do any and everything to get or have a man even if he's married. The men think that they are all that. He is only being used for what ever she wants him for so she doesn't have a problem with doing what they claim the wife won't do. Drop that zero and get yourself a hero.