That guy is a real piece of work. He was 50, married with 3 kids, and his wife was undergoing tests for possible cancer then. And I really don't know what kind of scum he is. People having affairs would already feel bad enough about it I would presume. This guy actually had my wife invite me out to social occasions with the two of them around, and would even shake my hand, buy me a beer, and talk to me with her next to us. And he would deliberately talk my wife out of meeting me when I was really stressed out and needing her (there was once when he did did when next to me when we had a phone conversation - he took her out on a yacht instead). Oh, he's very rich. One of the hooks he used was a partial share in one of the many companies he owns for her to run and expand.
So, he's deceitful, highly manipulative, and -- by definition -- a PREDATOR. And you're willing to gamble the future of your marriage on your wife being able to remain "just friends" and in contact with him??
It'll never work. The recidivism rate for infidelity is high enough, but without full "no contact" it's over 90%. It's only a matter of time.
Your wife will never begin to fully open herself back to you, emotionally, and you will never get the trust and healing YOU need without full no-contact and transparency. Considering your dalliance, you should offer mutual transparency.
Your wife already nearly burned down the house, and now you're letting her continue to play with matches.