I don't imagine that this challenge is very hard, and you seem to be handling it well.

If you still have Quake junctioned to Str (doubtful if you beat Disk 2), try winning many Abyss Worm cards, refining them into Windmills, and then in-turn refining the Windmills into Tornado spells. It's a tad bit more effective than Quake for junctioning.

Another easy spell to stock up on, and that's fairly useful for junctioning is Death (which can be refined from Chef's knife, which can be card modded from both Tonberries and Tonberry Kings).