I agree with Jgnat. Make him pay a lot and then NEVER see him again. His wife isn't your problem. She will figure it out one of these days as you did, and she's in for some unhappiness no matter what you do.
As for you, maybe get some counseling to see why you stuck with someone that sleazy for so long. Then you'll make better choices in the future. I'm not trying to be sarcastic, I'm serious. All of us need some counseling now and then to understand ourselves better.