Gunny The best chance to save your marriage is to give up all hopes of saving it. Yep you read right.
Don't become angry or vindictive, or hold resentments. Write her off as a loss. Think of the type of man that would attract a beautiful, loving, healthy woman and become that man.
To be honest the more I read your W's reasons the less I think it's about closure, but more about OM.
Let's face it for someone like OM to be "available" in this point in life means he must have his own issues, otherwise why isn't HE in a healthy relationship instead of pursuing a married woman.
He'll show his true colors, this fairy tale won't be all she thought it would be and she won't resist looking back at what she gave up for her so called fairy tale.
When she does look back, how will you look to her? Strong healthy deirable(even by other women) or sad mopey and pathetic.
Ok enough of that
What this means in real terms is get a life! Be happy, find happiness in yourself. I found one of my favorite hobbies during separation. It is now an integral part of my life, even after my W came back. She thinks were better for it too.