I haven't dealt with this sort of thing as a Photographer, but I have as the technical director of a large venue.
We would events ., fund raisers (losers) etc. booked and produced by everyone from the best most organized, to the worst.
Anytime any of the clients totally blew it, did not market the eent enough and therefore lost money, the firs thing that would take place was the leveling of blame on every one else involved, from us, the venue down to the there own light board operator etc...
Hacks all over this business. The trick is to spot them early on and not go forward with the event at all. Hard choices to do when your livelihood depends on it.
No advice from me, just saying, I know how it is!
However, I am more inclined to agree that the only option for you that makes any sense is to simply do nothing, and wait for an offer if they actually want the photos. My guess is they don;t, and they are trying to justify the lack of payment to you aggressively in advance, as they already know they intend to write the hole event off as a huge loss.

