Dang I'm really sorry. Sounds like she's trying really hard to put you between the proverberial rock and a hard place. But reading your original post, forgive me I haven't read the whole thread, kind of pisses me off at your ex.
How arrogant and condesending it is to want something like that in writing or to a third party?! Geez, what a cold and mean thing to demand.
It's up to you, but if it were me I would give her what she wants only if she gives me something in return. I would tell the third party (which leaves me open for plausible deniability later if I so choose) IF she paid me back all that "spousal maintenance". Otherwise go fly a kite.
Bottomline is I wouldn't give her what she wants unless you get something from her and that means more than just the absence of spousal maintenance.