Here's the list of level 3 spells...
And I agree with Vespasian, Difficult Spontaneous Magic is a pretty minor virtue. Just means you always divide by two; meaning you are always subject to botching and failure. Several characters I've designed can do a lot of level 3 effects without the need for any die roll, or checking for botch. And if time isn't an issue, Artes Liberales, Philosophaie and Ceremonial Casting can make more effects accessible, too. Without the need for fatigue, or a die roll or a chance of botching...
If you want a flaw that causes you trouble, try Weak Spontaneous Magic... Or don't take a Difficult or Weak Spontaneous Magic, and play around with some things...