I just read through your thread but mainly your posts. The reason your wife picked the OM is he is the kind of man who stands up for himself and takes what he wants. Your the kind of man who doesn't stand up for himself. He is an alpha male and you are a beta male. Simply put she can no longer stay with you because she feels sorrry for you.
You are a nice guy and thats breeds contempt in a woman.
You haven't said one thing in this thread that will help you save your family, you haven't listened to anything that might help you. You don't even have a Var in the car.
Buy this book and go to the blog. Married Man Sex Life | How to have the marriage you thought you were going to have. By which I mean doing it like rabbits.
( Its not a sex manual, it explains your relationships with women)
go here: No More Mr. Nice Guy
Your running out of time, but by her bedding you, you just might have a chance
Even if you can't save your marriage, reading these links/books will save your next one if you have the willpower.
I would wish you luck but you sound as if you have already thrown in the towel on your family.
Oh hell, Good luck