yeah, it's a heart breaker. I remember the feeling well (and I received it from WP, U of M, and Marine ROTC; not just USAFA). This is when the people who truly want it make themselves known and don't let the rejection get to them. I have been forever grateful for the opportunities that I have somehow been lucky enough to receive. Like I've said... Everything happens for a reason. Hope we're up to the challenges before us.
I know what you mean. But if you take the slot at USMMA, I don't think you would be able to reapply to AFA while you're at USMMA. That's part of my issue. I'm also a candidate for USMA and USNA. I decided that if I am not accepted to AFA but am accepted to one of the other two academies, I won't accept any appointments and try again for AFA next year. I REALLY want AFA. Does that make sense?
If want to game man that GPU/video card ain't going to cut it. Honestly, your specs aren't that bad for a surfing the web kind of PC but I think you are better off just buying a new system rather than overhauling. Also when you buy a new system make sure your power supply can support your GPU (500-700W) and really look at overclocking data as well as compatibility with processors. Toms Hardware puts out comparison and budget spreadsheets so you can best optimize price and performance. That's what I did with my 2009/2010ish rig and I can play games like Skyrim with max settings and din't have to drop a lot on a whole new system. When you piecemeal parts though you have to make sure each can support the overall system (i.e. motherboard, CPU, power supply etc)
Now...what would put your mind at ease? Probably nothing. I wish I could give you the "magic answer" and end the stress, I really do but honestly...I can't. From what you posted, you have a superb package!! And in most years in the past you would most likely be a "BFE recipient." But with the size of the class last year and this year...I can't even predict and I've been doing this since before you were born!
My "best advice" is to have a great final semester in high school, keep the faith, make sure your "plan B" is fully ready...and wait...I know that's MISERABLE...I've been through it twice when I applied to USAFA (and the others)...turned down once (still have the TWE's from all the SA's) and then when I finally received the BFE's from all the SA's (except USCGA...I was an alternate there; they are TOUGH!)