@Zadok: Thank you for viewing my video and responding! So let me answer your questions.
1) There is a limit to the amount of prep points you can accumulate. The limit increases as you level the Combo ability. So at level 1, the limit is 4 prep points and each prep rewards 1 prep point per round. As you begin to level, you receive more rewarded prep points per round, and the limit increases to match the increased cost of using the stronger abilities. It is possible to perform many lower attacks, by stringing together a 4 or 5 chain low-attack combination. But generally, your best bet is to use your strongest abilities. But this is not always the case. For example, I personally prefer Jaquio's third combo ability over all others because it does damage and heals him afterwards. So I incorporate that ability into most of the combo chains I do.
2) Unfortunately there are no team attacks. That would be awesome though!! The only team attacks that I can think of are done by the battle NCPs. Those are the guys that stand on the sideline as you fight. The above video actually shows one such battle NPC named Ashtar. In the scene that is portrayed in this video, you eventually gather up to three NCPs (Violet, Ashtar and Tau). Ashtar and Tau attack individually, but they also combine their attacks to do a more powerful attack. And Violet heals. Unfortunately, you cannot control these characters, and they are not in every battle sequence/scene. In fact, they are only in a couple scenes the entire game.