#1 - monsters on this part of the bridge(the mechanical ones) give very large amounts of experience.... level up, this is the best place to level up for a while to come.

#2 - Reflect or nul spells usually help avoid his powerful magic, but he can counterattack with flare.. which may one hit a character.

#3 - Overdrive Aeons = easy wins in most boss battles. Seymour can banish them, but if you get overdrive before the battle, your aeon gets at least one turn before Seymour can banish it.

This is the second fight with seymour, on the bridge, for the one asking.