What can I do on the ground in order to help my body acclimate to aerobatics?
The way the Air Force introduces people to the disorienting effects of aerobatics on the ground is to put them into smoothly spinning chairs called Barany Chairs.  And it doesn't just involve spinning in one direction, but smoothly and gently changing directions repeatedly.  Since I never suffered from airsickness, I don't know what they do (i.e. do they blindfold you, are there more than one axis of motion, do you have to tilt and move your head, etc.)

While an actual Barany Chair may be expensive, you could perhaps accomplish the same with  a friend and a nice heavy office chair.