It sounds like an obvious case of, “go screw yourself, you are not getting one red cent out of me. Try suing me, because you have an unenforceable contract” type of situation.
Lots of people ask for money they are not entitled to, just because they ask does not mean you need to pay. If there is an out for you written in the contract lean on it, and don’t let them scare you.
I have no patience for people you threaten others whom they have performed little or no service for. And I am a consultant by trade. I would never charge a client for a service they are truly unhappy with.
