No problem life. We've all been there. Been in the exact same place.
If I may help to clarify a few things and get them off the plate: OW - she is a symptom. Really. She is not the reason he left or does what he does. She'll end up with the worst of it once you get out of the way most likely. The anger? The feeling used? The feeling that it is so unfair? All part and parcel.
Will he feel the pain? Does he feel nothing now? Who knows? He may not or he may already. That's his journey and in His time your H will know the things he is meant to know.
Can't get around that regardless.
AJ
"Our lives begin to end the day we become silent about things that matter" MLK Put the glass down... "Yesterday I was clever so I wanted to change the world Today I am wise, so I am changing myself."
