$10 per character, in $40 byte intervals
Levels are -1, where 00 = level 1
Both should cap at $63
Shouldn't the levels cap at 0F, for 15? Max spell and weapon levels are 16.
On that note, having tampered with SRAM myself a bit to "fix" overmaxed HP, I thought it might be helpful to outline what hex values are needed as "caps" that the game doesn't already impose. While the game DOES prevent stats like Strength, Agility, Stamina, Spirit, Intellect, and presumably M.Power from going above 99, it still does level-up checks on them.
Spirit, Strength, and Intellect, at least, need to have their checks for leveling up skipped when they are at $63 (99), since there's no reason for them to be continuing to try to level up, and it results in you often losing Strength, Intellect, and Stamina accordingly. This can be applied to M.Power, Stamina and Agility as well, but they don't have any unwanted side effects of continuing to "level up" other than it being inconsistent were the other 3 stats fixed.
Weapon Skills aren't problematic either, other than the end-of-battle spam. Since they are using -1 value and starting at $00, $0F should translate to 16, at which point the check for weapon levels should not happen anymore, but they still do. There's also some sort of underflow bug based on battle rank with the weapon levels specifically at $0D and $0E, resulting in a single attack on a Rank 1 battle immediately leveling up the weapon skill.
Spell levels do appear to cap properly, as the experience counter will still go up to 98 or 99, but will never go up beyond that.
Scratch that, spells will also "level up" even at 16 if used enough times in battle, though it will simply reset the experience counter back to 00 in the magic window. This game just simply does not have hard caps for most things, with only a few mechanics in place to ensure that weapon and spell levels don't increment above 16 and stats don't increment above 99, while the math is still being calculated and messages displayed as if there were no caps.
Evasion and Magic Defense should cap at 16 (whether that's $0F or $10 I don't know), and I haven't tested if they can still go up. There'd be no easy way to test that, as there's no message stating they go up and you'd only be able to tell from looking at your stat windows 2 battles later.
For HP and MP, having already modified my SRAM to fix overmax, I can say that HP should cap at $0F27 (low byte then high byte) for 9999, and MP should cap at $E703 for 999. Currently it seems likely that these values would continue to level up to $FFFF and would no doubt overflow.