You definitely have a great profile, a fantastic GMAT, and some interesting extracurriculars to boot. I'm about to say something I don't get to say too often - I don't think you're aiming high enough. With your GMAT, status as underrepresented, undergraduate achievements, and your professional experience, I think your safeties can still be in the top 20. I don't believe you need to go below that (e.g. Kelley). You only do this once - go for it!
Also, as Christine mentioned, think hard about goal enablement. If your long term goal is to start that nonprofit (and hats off to you for that goal!) then Yale should be on your consideration set. Then again, if brand management is what you're all about then the schools need to match curriculum + opportunities +recruiting companies. All in all, I think there's a lot of additional work you can do to create a list of target schools that are perfect for you!
To your concern about the prestige - don't worry about that. It is what it is. It sounds like you're in a good spot now with a reputable company making an impact. If you left because of fit, that's a perfectly fine and mature reason.
If you have any questions or want to talk things through, I'm happy to chat with you!
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