Can you leave that place at that point? SOrry, but I don't really remember.Can you buy the ability distiller's from merchants? If you can, then just use those during battle. If you can't...hmm. A friend of mine had the same problem at the same part. But the part when you get ability spheres from a certain type of enemy comes right AFTER this part. I don't think there's anything you can do, unless what I suggested above is possible at this point.
I don't think you need that much for this battle. All you need is Rikku's steal ability, and possibly a couple of yuna's summons so that (SPOILER)anima doesn't do anything to you. This battle is all about strategy. If you play it right, you can take very minimal damage, and possibly none at all from Seymour. ( the nul-spells are the key). If you already knew all that, sorry, but I'm just trying to say that you really don't need too many abilities in order to win this. You should be fine.
