I only have a moment, G8, but you bring up an alternative option, and that is "the Sweetheart Deal." You could put a sweetheart (for you) deal in front of her, get her to sign off on it, divorce her, and then -- who knows -- maybe reconcile at some point down the line when she ends her affair or whatever funk it is she's going thru.
I really only recommend this when it's someone you really DON'T want to be married to, never WAS much of a good wife/mother, and when the deal is a real "sweetheart" one -- the one you describe sounds to me like the kind of fair, "50/50" deal you two should be talking about ANYWAY.
I'll check back with you later, but here's what I would ask you to help you decide: imagine yourself sitting down with your son, and he's 25 years old now. And he asks you "Dad, why didn't you fight harder for your marriage to Mom? Why did you just give her what she wanted, when you knew divorce would be bad on the whole family?" You'll want to have some DAMNED GOOD, be-able-to-look-him-in-the-eyes answers on that day, G8.
