As for the percentage of health setting, I dont really remember exactly (not in game atm), but its somewhere in the character settings, probably an option either on the general tabs, or UI tabs. Also, as I normally play with a gamepad, I dont have problems cycling monsters, other than what I wrote before I dont think I can help much T.T From what I know, the cycling (tab) is always left to right, not from close to far, so if you have a close, far, close enemies, it will tab it like so from your character perspective, so try to line yourself at an angle you want to tab the enemies.

As for enmity, as PLD, I wil cycle through every aggro'd enemy and check the enmity bar manually, while attacking them with the hate bulding combo, then returning to the main monster. Also, remember you can mark the monsters, there is a filter that can be put that let you cycle through marked things only. I think tabbing will go 1,2,3,etc, regarding of close/far the monsters are, but I dont really know if thats the truth or just lucky when I cycle the marked monsters lol.