Nate, I'm glad to hear that you're taking care of yourself!
I'm with Sandi on trying to contact a L. You don't want all of your conversations with WW to revolve around divorce, selling the house, etc. If she starts to bring that stuff up, I'd tell her to just let the Ls handle it and that you don't want to talk about it. Keep yourself out of it as much as possible.
I don't think there's anything wrong with sending a few truth darts her way, and OM and his S should definitely NOT be at the B-day party if you're going to be there. I'd hold firm on that one, but you have some time before that happens as well.
Remember that the housing market is down right now because of the recession, so even if the house is appraised high, it doesn't mean that it will sell right away.