Not at all. (:
Somewhat. Things you wouldn't even think affect the ending kind of do. If you don't want the bad ending, just remember that you have to lose a certain battle at the end of the game. It should be obvious which when the time comes.
Good luck then~
Keep in mind that there are multiple endings. I'd suggest staying away from the bad one, it's pretty sucky. And sorry for ranting, this game does that to me. xD
The story's the best part~
Wait until you beat it, it has one of the most memorable endings I've seen. Then again I'm sentimental as hell, so... don't take my word for it.