Great to hear you're planning in 8th grade.
First of all, while USAFA might put some weight on Marching Band, it's not a sport (at least where I live). Golf is a sport, and marching band is not - I know, I asked that question many times. Also, Marching Band does not allow for you missing practices, as you leave a hole in a formation that screws everything else up. Bottom line - during Marching Band season, you have nothing else to do. Additionally, most MB members also had band as a class, and were strongly encouraged to join Pep Band (a half dozen or so musicians at every sports games, cheering them on)
A typical rotation of activities (in my DS experience) was Marching Band in the late summer and fall. Swim team over winter, and one of cross country, golf, or tennis in the spring. Note that all of these are individual sports, rather than team sports (and I think I've read the academies want to see a team sport. Are you good enough to make your baseball/softball team in the spring? You might want to work on it to get a true team sport under your belt.
Now your BJJ isn't a recognized sport in our school system, but should serve you well should you take up wrestling (again, an individual sport versus team).
Let's complicate things with JROTC. DS was told as a rising freshman, there was no extracurricular time required, but guess what? To advance well in JROTC, he needed to do Raiders or Drill (much extracurricular time, and with drill, you can't miss practice for the same reason as Marching Band).
Next is your community involvement. You don't mention Boy/Girl Scouts, girl Boy Scouts, 4-H, AHG or church youth group (actually out doing things).
The point being, yeah, you need to map out the seasons and pick your schedules carefully.