Colly pointed out that the Kernel of the NTSC-U version is different in structure than the kernel of other versions including pc releases. I do not know how much of this is already known as the wiki section about this is all empty.
Inside the Kernel File, spell data starts at 0x246. Each Spell has 60 bytes so calculating the position of a spell is taking the ID, multiplying it by 0x3c and adding that to 0x246.
If spell ID is greater than 24 0x130 has to be added because from 0x800-0x930 there is pointless data right inside Full-Life.
Inside a spell description there is:
0x1A: Damage Constant
0x29-0x31: HP-STR-VIT-MAG-SPR-SPD-EVA-HIT-LUCK
The junction values for eva are higher than on wikis or gamefaqs as they just see how Evasion changes and thus have wrong values. This is due to the way the game determines evasion stat.
After the junction values there are a few bytes for Status-J and Elemental-J. Im not perfectly sure yet what is what but Status Junction is first.
Spell ID List:
0-8: Fire, Fira, Firaga, Blizzard, Blizzara, Blizzaga, Thunder, Thundara, Thundaga
9-17: Water, Aero, Bio, Demi, Holy, Flare, Meteor, Quake, Tornado
18-26: Ultima, Apocalypse, Cure, Cura, Curaga, Life, Full-Life, Regen, Esuna
27-35: Dispel, Protect, Shell, Reflect, Aura, Double, Triple, Haste, Slow
36-44: Stop, Blind, Confuse, Sleep, Silence, Break, Death, Drain, Pain
45-49: Berserk, Float, Zombie, Meltdown, Scan
50-55: Full-Cure, Wall, Rapture, Percent, Catastrophe, The End
I also located limit breaks, Ill keep this updated.