1+2. They're just differences between the FMV and in-game models. They're not going to redesign Aerith's model just because something happened in a FMV.
3. They didn't want to give the game a 15 rating. Anyway, it would've spoiled the perception of Aerith being the embodiment of that is good and innocent.
5. Simple - he's not the last of his kind.
6. Tseng didn't die, he was merely wounded. See 7.
7. Spelling, grammar and translation mistakes are rampant throughout the game.
9. Doesn't look like there's anything wrong with it to me.