Erm... you need a good junction, i.e. a lot of str for Squall. Try casting Aura at him and making as many Renzokukens as you can. Also, I'd strongly suggest having Quistis with White Wind and Guardian or Selphie with Full Cure in your team.

And yes, try getting 9999 HP for everyone

I've beaten the game a couple of times. The easies one was with Squall and Quistis at level 100 and Selphie at level 87. 2 healers and one strong attacker just rule