Since the HP codes aren't exactly working properly for the game or the way people intended it (rather than only being healed when accessing the menu), you might as well just give yourself all the equipments so you won't take damage. Keep a crappy sword if you want the fights to last a while, but use the armor/accessories to prevent taking high damage, and also increase your base HP that way.
Code:
// ----------------------------------
// [Equipment Codes] ----------------
// ----------------------------------
// All Keyblades
patch=1,EE,103F217A,extended,00000101
patch=1,EE,403F217C,extended,00030001
patch=1,EE,01010101,extended,00000000
patch=1,EE,103F218C,extended,00000101
// All Staffs
patch=1,EE,403F2190,extended,00030001
patch=1,EE,01010101,extended,00000000
patch=1,EE,003F219C,extended,00000001
// All Shields
patch=1,EE,403F21A0,extended,00030001
patch=1,EE,01010101,extended,00000000
patch=1,EE,003F21AC,extended,00000001
// All Accessories (X98)
patch=1,EE,103F213A,extended,00006262
patch=1,EE,403F213C,extended,00090001
patch=1,EE,62626262,extended,00000000
patch=1,EE,003F2160,extended,00000062