You find another Ring of Wizardry on a Harper mage when fighting Jaheiras "friends".

Killing Kangaxx is easy. When he turns into a demi-lich, cast Spell Immunity Abjuration on yourself, then just use Melf's Minute Meteors on him. It will take a lot of meteors, so you may have to cast Spell Immunity again. That's how I did, and finished him off with Ring of Ram. Level???? As soon as you can cast both Spell Immunity and Melf's Meteors.