If you confront her, then I think she will feel pressured to make a decision at that moment! The night the stuff hit the fan at my house.....I left. I felt I "had" to do something. I believe your W will make a decision you will not like. I did come back b/c there were other things I was forced to consider (and won't get into all of that)but if it had not been for the "circumstances".....I would not have returned. So, keep that in mind "if" you confront her.
I know you are angry and you have every right to feel as you do. But as it has been pointed out....she is not the same person you fell in love with & married. Do not expect her to act like the person you've known. I am concerned about you getting into a fight with her when you know in advance that she will be p*ssed. It's like you want a boxing match, trying to get your anger out. Don't fight the person in the R, but fight for the R. Big difference!
When your emotions are charged, the brain shuts down. It may feel as if its going 90 MPH.....but you won't make good decisions. I think the book says to take 24 (or is it 48?) hours before doing anything.
Don't confront OM.......and forget about what you could do with his n*ts......b/c he's not worth fish bait....(or whatever it was you guys were talking about).
Remember what type of character the OM has if he's playing around with a M woman! He won't care what you threaten or how tough you may sound! He's dirt! I read the same stuff when I first came on board and I did not want to believe that about "my" OM. He was different! Yeah, right. I was so addicted that I could not see him for what he truly was. Your W is the same way and you must think of her as an addict. How would you handle the situation if she was on drugs? Maybe differenly.....maybe not, but you need to try to calm down and think this through before acting on your emotions.
You need to do some extreme physical workout to get this anger out of your system or you will continue to fight with your W. It is fine to come here to vent. You "need" to vent here and not to her.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!