You guys crack me up. It's pretty cut and dried, you didn't screen for DH. It doesn't matter if you "took no action", you're ineligible for DH. It doesn't matter if you actually FOSx2, or just resigned. Continued bonus payments are contingent on you screening for and completing a DH tour.
Edit: the payment you would have had to pay back if you would have left before March was contingent on you completing that year. I really don't get the thrust of your argument here. Besides, from what you've claimed, you're already enjoying a "lucrative" contract, so what's the big deal?
If you really had a legal leg to stand on, you'd take it to court. Seems like the $25K payoff would make that process worth your while. The fact that a JAG won't touch this tells you everything you need to know about the merits of your case.
Brett