You don't actually need to break hp limit, infact I'd advise against it. Unless you do the Dark Yojimbo reset trick, getting dark matter can be extremely longwinded & tedious.
Just max stats (except magic, that too is pointless, long winded & not needed), and cast Auto-Life. You will beat him. I have beaten every enemy in the game, including Dark Aeon's, with not one character with Break HP Limit.
Quick Hits & Auto-Life are your eternal friend.