The part about him going back to the OW right after he says he wants to work it out with you. It's especially tempting when they work together. Sometimes I get chastised for recommending that the cheating spouse should find another job away from the OP. But why risk the temptation?
I don't know why you'd get chastised for that, Bond -- it's darned good advice. If you are a recovering alcoholic, do you keep liquor in the house? Do you take a job in a bar?
I have even seen it advocated that the reconciling couple MOVE TO A NEW CITY in order to ensure no-contact, and that they have every opportunity to try to heal their marriage, unencumbered. My wife and I didn't have to do that, but she DID have to quit her job (a boundary of mine), and she agreed. To do less is just letting the recovering pyromaniac play with the matches and kerosene.