I get the desperation, I really do. But telling the OW that she can have your WH if she tells you they've had contact almost guarantees that you'll not get the truth, and you also will forever wonder if she lied about the continued contact in order to get your WH. It's a no win situation, unfortunately you can't take it back now.
But, that wasn't what my WH and he's spent the last year showing me that.
Tell your WH he's free, tell the OW she can have him. If he wants back in he'll have a lot of work to do.