No company is going to go to FW after 2 rounds of negotiating lol.. the first offer will always be low, although it seems the subsequent offer made by Virgin was even worse.. Pilots needs to stand up for themselves. I agree with the OP, call their bluff, that's the only way they're going to come back with better terms.
Consider contributing some $$ into the kitty and taking all the info to a lawyer to get some impartial legal advice. It's shocking the unions are endorsing it after the second round of negotiations.. they sound like they're over it too..