I agree, fights are surprisingly difficult - enemies do pack quite a punch - before you reach top level. I don't know anything about cheat codes but I can give you this tips :
1) Grind. It's boring but since each level up give you tremendous health bonus, it's the only way. You can rampage through the forests as much as you want (fights do not cost time) and I didn't notice any negative consequence to lose a fight : you'll be back in Meridian with full health, sooo... go PvE !
2) You get a significant bonus in health and damage (or so it seems for the latter) when you transform. Transformation costs 50 MPs and lasts 3 rounds, so your basic plan is to get these 50 MPs the quicker and make the rounds count. MPs come from attacking AND blocking.
3) Don't be afraid to bully. Despite what the game seems to imply, fighting monsters of your level is not a balanced fight (like I said, monsters hit heavier than you). So go hunt for rebels even after reaching fourth level.
I hope this help.
