Status spells are mainly affected by Faith, both the caster's and the target's. The higher the Faith, the higher rate of success for status spells. More MA (Magic Attack) will also raise your chances of hitting with a status spell.

You can use Magic Sword with any Job, actually. The only requirement for using that skillset is that you have a sword equipped. So, if the Job doesn't naturally use swords, just use Equip Sword as your support ability.