So Final Fantasy IV was one of the few in the series that I have never gotten around to beating so i decided to make that my mission. So I am hacking away at the game and so forth and i am at the Tower of Zot and honestly I'm getting killed by the enemies in the tower its not that i can't defeat the random encounters its just that after two at the most i have to retreat back to town and use the inn. My levels are

Cecil lvl 18 HP 976 MP 78
Yang lvl 19 HP 814 MP 0
Cid lvl 21 HP 857 MP 0
Tellah lvl 22 HP 392 MP 90

so what I am asking I suppose is your opinions on how high leveled my party should be. Also any other leveling tips or advice you can give WOULD BE GREAT!