Diablo 1 HD Hellfire Mod | Awake

Title says all.
I wonder if i can level up my apocalypse spel(and other magic-heavy spells)l to 15 with it.

There isn't.

I think there is, if i understand you right. Just yesterday i had an enchanted cauldron (spells +2 lvl) in Horazons Sanctum.

That's a Lore shrine, only temporarily gives +2 all spells.