I would get all the details you can from OM's wife. But you don't need to explain stuff in detail to your wife. Just let her know you know she is a liar, and stand firm on that. Look her in the eye. Let her know how disgusting it is. You do not explain how you know, what you know, or go into details.
And if your W begs for another chance, the answer is not yes or no, not right now.
Take some time and space and get away from this for a while. Can you get out of town for a few days?
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.