I understand your hurting and your sitch is bad, it is bad for the kids, you and of course your W. Have you ever asked her why she is seeking the comfort of another. Based on what I have read of your sitch you want to work it out but you are pissed her affair of the end of it is not meeting your timeline.
I will just say this think of this like alcholism, she won't quit until she is ready to do it herself. I don't blame you for your actions and your feelings of anger and punishment are very understandable. Nobody likes to feel like a doormat, but blowing her up is going to help who and for how long. Maybe you will feel good for a few months but what about the kids and what about your W. What will happen to her as her world collapses.
I will offer this if you make an ultimatium before you file, ask her to seek individual counseling. Let her figure out what it is she needs to get herself right, sounds like she is very confused and very screwed up. She doesn't sound like she has much in the way of self confidence.
I wish you and your family well.
Married:10 years D final 8/28/08 10 minutes is all it took Life goes on and DB was no small part in growing from the Divorce!