Generally, people who want aviation get aviation unless they are really low in the class. Some may get NFO instead of pilot, but the majority of people who want pilot...get pilot. Don't suck and you'll be fine.
An aero degree may help a little bit, but the level of math and engineering you encounter in flight school is actually pretty low. Any degree from the Academy has sufficient STEM requirements to get you where you need to be. Not to mention, stick skills/procedures are the biggest factor for how you do.
They are very accomodating about motion sickness. Probably half my class got actively airsick (i.e., puking) and most people were passively sick (nauseous). I'm the exception in that I've felt fine every time I've gone up...and I have gotten seasick before.
If you continue to get airsick past the first few flights, they'll first give you airsickness drugs. If those don't work, they'll put you in the spin chair and basically force the airsickness out of you, or get you extra flights for acclimation. It is extremely rare that someone is dropped for airsickness.
