Puppy, I have no motive here other than saving my M. The separation we have agreed to includes no alimony and fair division of prop. In fact i will come out better.
If that's indeed the case, then my advice to you is drastically different. I think you should take the agreement and run.
You can always do intel after the D, and try to expose her back toward you, or you could simply wait for the affair to run its course. But you would have a sweetheart deal in your hip pocket, and you'd be a "free man" and dealing from a position of strategic strength.
Keep in mind, that advice is PURELY strategic/tactical advice. It doesn't really take your HEART into account, admittedly.