Alright, first things first, you're people are too low leveled. Second of all I highly reccomend you go to Eureka! first and load up on shurikens and get all the special weapons there. Personally my winning party is a magus, knight, ninja, and a sage, all around level 60. If you have onion knight and the job level is very high I highly reccomend using them.

Also when you finish the game you start back at the last place you saved... BUT next time you save there will be 3 stars on your save file and you get a crystal helm, crystal armour, and crystal gloves.

P.S There is no connection between FFIII and FFIV so you should get it wether you finish it or not, cause it's an awesome game.