The App Store is only viable because Apple is protecting it as a crown jewel loss-leader. If the Store were spun off into a separate company (not a subsidiary) that had to be profitable on its own, I can imagine the policies changing for the better rather quickly.
I don't think it's a protection thing, and loss-leader isn't entirely fair. The App Store makes money, there's no question about that. It's just that the profits from the hardware make the App Store money irrelevant. Apple almost certainly makes more money from the Google Searches in Safari (maybe even just in MobileSafari) then they do from the App Store, figures in the hundreds of millions. Compare that to the iPhone profits which are in the billions already.
Unlikely. 30% is already pretty high, probably more than any startup would have been able to credibly command. It's another instance of the lack of choice allowing Apple to dictate whatever terms they like, however unfavorable they may be.
