I recommend turning Arc into a Devout. Not only will he be ten times more adorable, he'll have many more MP charges devoted to White Magic. Since Refia is your offensive spellcaster, you should have a good healer.

Have Arc heal every turn. With either Curaga, or Curaja when everyone gets down. Have Luneth Jump, of course. Have Ingus throw Shuriken. This party doesn't need Haste or Bacchus' Wine. Have Refia use her most powerful summons, but have her use items when necessary. If someone dies, try using a Phoenix Down on them, but don't stop the healing. They might get healed by spam healing when they get revived, if you absolutely can't spare a turn for Arise. Remember, the first priority is getting everyone healed every turn.

Also, make sure to get four Ribbons to protect against Bad Breath.