EDIT:
How can I change the enemies stats as well? HP, STR and others?
For this you need another tool, Ifrit. It can edit the various com.dat files inside the battle.fs (don't remember if you need to extract them first, though, it's been a while since I last used it). Anyway the files com000.dat to com143.dat each contain one enemy from the game.i'm working on a mod that i'm already up to v12 on, where the main thing i've done is Fixed all the Stats that originally weren't going up as the bosses / enemies level... if you wanna try it out, otherwise make sure you backup all files... cause ifrit has been giving me issues on about 3 bosses + a few randoms... where i got corrupted files and had to restore the orig... one of them i've tried a few times but no luck so far at making my changes without breaking it, luckily it's not a big deal for the one in question...