u can beat it at a fairly low level but its made even easier by the a liitle sneaky method. casting(SPOILER)Vanish, followed by doom will kill most bosses. the exceptions being undead, machines and really powerful bosses .

the hp is not low at all.it should increase to a quite decent lv over time. however 2 get near 9999 hp, u will need 2 use esper hp bonuses.

hope thats a help. dont worry, ffVI is one of the easiest ff games.