The NG will release Soldiers for USMAPS, but I wouldn't put your eggs in that basket. Not saying one way or the other, but:
1) have you completed basic? If not, they aren't going to consider you a Soldier for admissions purposes. That would definitely impact your chances of USMAPS.
2) generally, SMP cadets aren't looked upon favorably to use Soldier billets, because they are really just ROTC cadets who have or will do basic that summer, drill as a LT, and get paid extra for it. Doesn't sound very Soldiery does it? How's your relationship with the Soldier/NG RC? What have they been saying?
3) if you are SMP, that generally means that you are already in the ROTC pipeline for commissioning, which in and of itself pretty much means you won't go to USMAPS. Why would USMA take you out of ROTC in which the Army will have a 2LT in 3 or 4 years, say you aren't academically qualified to come into WP (especially if you are successful in/accepted to ROTC), and send you to USMAPS basically putting you on a 5 year path to commissioning? Conversely, if you really aren't academically qualified while trying to make it through ROTC, why would USMA want to take a chance on you when you are demonstrating that you can't hack it? What does your ROTC nomination say? What does your company commander's nomination say? Poor performance in academics usually will result in a poor nomination write up or refusing to give the nomination, which in turn says something about your chances.