I don't remember what the average MCAT and GPAs are anymore for usuhs. However, usuhs loves prior service people! And you are medical prior service so that'll be a huge plus too. It sounds like you've learned the hard way about taking on too much, but it also sounds like it didn't hurt you too much. Bs are fine; I had a couple of Cs on my college transcripts (one of them in an upper level bio lab class). Just try to not take on too much in the future and do your best to get A's in bio II and chem II. Also, try to take breaks and such - don't stress yourself out too much over all of this. Try not to fret too much about what's over and done with, the only thing you can do about the past is learn from it. Take your time to study for the MCAT, especially if you're like me and are horrible at standardized exams.
In terms of deciding on programs, I don't know much about the others, but I do know that a lot of prior service people will choose usuhs for some of its benefits. Mainly, they're a lot closer to retirement and your 4 years at usuhs count toward your time in service once you hit 20 years (i.e. if you get out at 16 years, your 4 years at usuhs won't bump you to 20, but once you hit 20 you'll automatically get bumped to 24). That and most of them have families so being paid as active duty is helpful (especially for the prior officers who have save pay, but you would also get a bump in your O1 paycheck by being O1/E).