I still can't see how she thought what she was doing was a good idea, though. That's part of the problem for me...when I look at that, I just see her as a major train wreck...and it's hard to love a train wreck.
I really like that your MC has your wife focusing on respect. That's very good...
I definitely understand your feelings about how the S could make this decision in the first place. One thing I like about the "Not Just Friends" book it explains how easily these affiars can occur even in good marriages (by people who don't believe affairs are right!). According to the book the whole thing is not recognizing or holding to boundries, and this can happen much more easily then expected. There's a really good example in the book describing a relationship gradually going that direction.
We can look in it in a technical psycho-analytical manner, but I know when it boils down to it the whole thing hurts. It's a betrayal by someone we trusted and that's hard. Even when you understand how it can occur (which does help a little!).
I think this is our challenge, in the long run we'll learn a lot and become stronger people even though it hurts.
Here I talk, but my husband's not even in the house committed to working on things yet. We're only talking about "possible reconciliation." I have to say I do respect your wife for doing what's right and coming back to you. I don't think it's easy for them either. But time really will help.
There is no arriving, ever. It is all a continual becoming.