I have Auron on 33.000, Yuna on 30.000 and the others have yet to have break HP limit.
Everyone as break damage limit to 99.999 and i pretty much finished the sphere grid for everyone except Rikku.
The aeons are from 15-37.000 hp and do all 99.999 and every stats is pretty much above 200 and most of them 255 with both characters and aeons.