I can sympathize. The exact same thing happened to me. My H was supposed to sign our Agreement (that we reached in court!) at 3pm to be filed at 5pm and he backed out.
I went hardcore (he was paying the legal fees, lol, so why the hell not!) and the night before our trial was to begin he backed down and signed. I waited until the very end to pull all out ALL the cards I had and while it was a bit of a gamble in the end it worked in my favor.
If you do retain your attny (I agree, mediation is a joke) be sure he contacts your W's attny and tells him/her ANY future contact must go through counsel.
Sending you tons of good vibes - I have been where you are and it is pure crap!
