Why? If you want real
revenge, that will involve things that will result in public humiliation, social death, and career disaster.
If you're going to Get Back, do it on a professional level ... cheating is for kindergarteners.
For me, I'd just dump his disrespectful ass and get a blood test to make sure I didn't get anything. I'm not sure how cheating would hurt a cheater since they find nothing wrong with it to begin with - it just verifies and condones their own bad behavior with you since you'd be doing it, too. Logical? QED.