There are some things in your life you never want to try. So, to make this painfully clear, I'm going to write a short little letter (this is how I manage to not bottle up rage and anger, so don't think I'm like this in person. I'm actually nice. Honest.)
I understand that you took a loss on your house. Probably everyone else selling right now has too. Whatever your reasons are for moving, they are not my problem. I have too many of my own concerns to deal with to take up a cross that is not mine.
That being said, seriously? There are some things in life you don't want to try. The most famous is never get involved in a land war in Asia, but only slightly less well known is this (Princess Bride. Go watch. Now.): Don't try to weasel your way out of a contract where the other contracting parties are two lawyers. One of whom just took the bar, so has all that fabulous knowledge about real estate and contracts and SPECIFIC PERFORMANCE still crammed in her brain.
It's in the contract. We all signed it. You have to do it, or we (and note, this is not because we are lawyers, anyone could do this) can and will sue you to get this house. Fair's fair. Grow up. Pony up.