The best part was the music at the end. Epic music
Good concept, you just didn't do anything with it. If you were going to parody FMA, then you should have made it feel like FMA. An animation called "divided by zero" did a very good job of maintaining the 300 feeling because they stayed true to the the driving force behind that movie. Action.
If you had thrown in a bit of sound effects when the Elric brothers divided by zero, changed the background music when the arms came out of the blackboard, maybe something akin to a struggle when their bodies were being snatched, ect, ect, so on and so forth... anything to make it feel a little like FMA, not just some mathlete nerds playing with numbers.
Nice try though.