I don't know exactly where each character's data block begins and ends. For the first character, the first value I know is current HP at 172-173, and the last value I know is maximum MP at 1FF-200. I do know that each character's data takes up FF bytes.
Important: All these following addresses will be for the first character's data. If you want to hack the second character's data, add FF to the address. If you want to hack the third character, add 1FE. For instance, character one's current HP is at 172-173; character two's is at 271-272, and character three's is at 370-371.
172-173 Current HP 1FD-1FE Max HP 174-175 Current MP 1FF-200 Max MP 176 Strength 177 Agility 178 Vitality 179 Intelligence 17A Spirit 17B Luck 18A Experience level 17C-17D Total experience / 50000 17E-17F Remainder of (total experience / 50000) 186-187 Exp. for next level / 50000 188-189 Remainder of (exp. for next level / 50000)
No idea why exp. is stored like that.
1A7-1A8 Attack power 1AE Evade rate 1AF-1B0 Defense power 1B1-1B2 Magic defense power
These are determined by your stats and equipment, so any changes to these won't be permanent.
18F Weapon 1B5-1BB Spare weapons
A value of 00 is Nothing. 01-1E are swords. 1F-2A are cool-looking "Nothing" swords with varying attack power. ^_^ Each character's weapons take up 2A values: 01 is the first sword, 2B is the first glove, 55 is the first dagger, 7F is the first rod, A9 is the first flail, and D3 is the first spear. Sorry, no matter what weapon a character is equipped with, they'll look and fight the same as ever.
190 Helmet 1C5-1CB Spare helmets 191 Armor 1CD-1D3 Spare armor 192 Ring 1D5-1DB Spare rings 193 Shield 1DD-1E3 Spare shields
00 is Nothing. 01-48 are helmets; each character takes up C values. 49-7E are rings; each character takes up 9 values. 7F-F6 are armor; each character takes up 14h values. F7-FF are all shields! (I wonder if they're all available in the actual game.) Notice that you can put any armor type in any spot, which can lead to strange stats.
1E5-1F0 Spells
00 is no spell. 01-06 are Diamond Missile, Earthquake, Stone Cloud, Protect Up, Speed Down, and Diamond Saber. The other elements follow the same pattern as much as possible. 07 is the start of Air, 0D Water, 13 Fire, 19 Dark, 1F Light, 25 Moon, and 2B Tree. 31 is Detect, which was apparently dummied out and has no description or effect. 32-4F are assorted spells and techniques. 50-79 are second and third level power attacks, which you can "cast" for 0 MP. (Be warned that if the "wrong" character uses an attack, it'll look funny at best, and crash the game at worst.) 7A-83 are thrown weapons. 84-AE, B6-CF, and D4-DA are (drum roll) enemies' special attacks (and trap effects, etc.). Like character techs, they don't consume any MP. (A couple notables: 9B Hyper Cannon, 9C Hell Southern Cross, A3 Mr. Death God, B9 Spiral Moon, and CF Flare.) 93 is Black Rain, whatever it's doing mixed in there. AF-B5 are "magicXX's," visual effects for bosses dying. D0-D3 and DB-FF are "SBD's," most of which are just visual effects. (Two notables: E7 leave area, E8 call Flammie.)
1F1-1FC Spell targeting values
01 is One, 02 is All, 03 is One/All, and 04 is caster (for ally-targeted spells) or last ally targeted (for enemy-targeted spells).
Any character can be any class. The three class bytes determine what spells a character learns, what second- and third-level special attacks they have, which set of weapons and armor they can equip, and their color scheme. They apparently do NOT affect which set of equipment shops will sell you, although the light-dark scale does determine whether the later shops will sell you light or dark equipment.
18C Class family (base class) 18D Class changes 18E Light-dark scale 185 Counter gauge maximum (04, 07, or 09)
Class family is a value from 00 to 05, with 00 being the Fighter classes, 01 being the Grappler classes, and so on. Class changes is 00 for the base class, 01 for a second-level class, and 02 for a third-level class. Light-dark scale can range between 00 and 03, with 00 being light-light and 03 being dark-dark. For example, a Thief would be 02 00 00, a Ranger would be 02 01 00, a Ninja would be 02 01 01, a Nightblade would be 02 02 03, a Magician would be 03 00 00, etc. etc. Happy changing!