Please don't bury your head in the sand OP. A few months ago I found out that my H was having an affair in cyberspace with a girl he had med through work. They only met that one initial time but we both agree that he has been unfaithful to me, but I see that you don't need convincing of that.
I was / am devastated. He realises his stupidity and we are both working hard (especially him) to repair the damage. The one thing I am grateful for is that since his confession he has, as far as I know, been completely honest with me. There was nothing wrong with our marriage before his affair but he inflicted damage to it when he started to detach from me and our children though guilt and plain selfishness.
Had he not come out with the truth eventually we wouldn't have had a chance to repair that damage and I believe that our marriage would have spiraled into decline. Your husband can't help you through this unless he knows the truth. From my experience, truth is the only option.
As far as the OM's wife is concerned I couldn't say if she will contact your H. I contacted the OW but it never occurred to me to contact her partner.
I didn't even know that this OW existed before but it didn't take me long to find out her phone numbers, her address, her email, who her friends are, her partner's name and where he works. No matter what steps you have taken to remain anonymous, she'll find out who you are if she wants to. It's not rocket science.
By the way, I didn't find all this out so I could stalk her or do anything else sinister, I just wanted to know more about her.