Darkside damage seems a bit awkward to modify. You could try:
0x91069 = 8D 34 B6
(or 0x491069 if the game is running)
That should boost the damage by 33%. Unmodified, Squall dealt 400 damage with Darkside which went up to 600 damage with the above change.
Way it looks in assembly is:
It can be put up one more time with:
0x91069 = 8D 34 F6
The damage dealt with that is 1100, but increasing it past that will probably need more involved adjustments unless there's a different place where the damage can be increased.