You have a pretty good case for the IG due to the stonewalling of not getting a signature on 1 and 2 QTR FY 18. Unless the non-signature is for cause (pending FEB, MEB, admin UCMJ action), they're gonna have to honor your November date, which would fall well before the 4 April date they have given as the deadline for honoring requests. But we simply don't know the circumstances behind your loss of qualification. That may be the sticking point and you may not want to expand about it on here, which is certainly your prerogative.
As to the practical implications of this scenario? Just like @SocialD described, it's basically high time to idle-boards participation. UTAs are the only required periods needed to gain a good Reserve year, and AT are the only days your SQ/CC can legally compel you to the squadron and away from your civilian responsibilities (plus the MUTA(s)). If you've already burn those, they can't do fog all. For someone who is already dead to the unit due to the loss of qualification, this is only being done to pad the numbers. What is most likely to happen is you'll submit your IG, everybody will get umbraged, you'll get your signature effective 1 Oct 18. Then, just like two years ago, loss management will get lifted on 1 Oct 18 and you'll be on your way out. I don't have any reason to believe based on earlier loss management that they will concurrently implement loss management on 1 Oct 18 to keep folks for the entire FY 19. Usually these implementations have happened mid-FY, just like this one.
Personally I think it's a complete loss on everybody's part that people end their service tenure on such jaded and toxic terms. It truly is a loss for everybody involved. Then again I've also encountered the opposite, people whose attitude is so price-elastic that the second they make a nickel an hour more per duty period at the airline than at the unit, having two jobs is all of a sudden the biggest affront to their livelihoods and the welfare of their children you could ever impose on them. It's a bit much sometimes. That said, the invol IA BS is what's killing manning these days, I'd say even above and beyond TSPs and/or unit-wide mobs.