what minimum level and stats do you reckon that i should have in order to memorize at least 3 slots of level 9 spells?

last time i finished the game (a year ago iirc) as a mage i couldn't even have one slot of level 9 spell memorized, despite really high INT & WIS (around 24).

There are some tables in the appendices of the manual that might help. I'm not sure if I read them correctly, but it seems that you need to have intelligence at 18 to be able to learn level nine spells. At character level 18 you get the first slot for level nine spells and at level 22 you should have three slots. High wisdom seems to give bonus spells, but not for the ninth level.

Wisdom doesn't grant bonus spells and int doesn't affect spell memorization. Wis grants bonus XP however.
It's possible to finish the game with less than 3,000,000 XP and therefore no level 9 spells, if you insist on high level just dismiss your party members and solo parts of the game.

i suppose you're correct. i finished the game last time around char. level 22 iirc, with full party. meh, i'll play as a fighter now. more fun.