As a seasoned veteran of the park:
I wouldn't worry about crowds on Tuesday August 20. First day of school for Prince George County, MD (the county where SFA is located) is August 19. I'd be more worried about the park having enough staff to run the rides.
Flat rides - Nothing particular about flat rides. If you don't mind wateparks, Bonzai Pipeline is pretty good.
I think your pretty far off on where to ride:
Superman:ROS gives lots of airtime in the front and a spectacular view going up the lift. I seem to sink in my sit in the back, never understand the fascination with the back of the ride.
Joker's Jinx: Could go either way.
Wild One: If you don't mind getting banged around the back. The front I feel is better.
Apocalypse: Do not do anything other than first two rows. You will bash your head into the restraints.
Mind Eraser: Best in the back. Not as much head banging.
Batwing: I like the back a little more than the front. Your on your back up the lift and the front pulls you over the top and flips you a lot faster.
Roar: Your going to get banged around where ever you sit, but I would ride in the front.
Above average food places: Not at SFA. Everything is pretty average or below average. BBQ Sandwich in Coyote Creek Restaurant is ok. I understand the pasta in Heritage House is decent.