Can DBing backfire? Could he think I'm so indifferent that it pushes him to OW? H is a very needy person that needs reassurance all the time.
I know it seems counterinutive but affair busting works exactly the way you described it. Pushing him towards the OW is exactly what you want. It is the only way that he may look within himself to see that the OW is not the answer to his PAIN.