Think of it as an addiction. When you take the drug away from him he wants it more. The OW is his crutch. So unless you can arrange for a major intervention, he's going to keep going back to the OW.

Would his family be willing to stage an affair intervention?

M-43 W-40
2D - 9 and 5

Emotion, yet peace.
Ignorance, yet knowledge.
Passion, yet serenity.
Chaos, yet harmony.
Death, yet a new life.

RECONCILED AND WISER