[ericthered]

If that's what you have, its because you've dumped an exceptional number of points into disadvantages.

The point expenditures you described so far:

IQ 20 [200]
Magery 3 [35]
50 Spells [50]
2-dozen IQ skills [25]

That's a total of [310] points, and you started with [180]. That means you have [-130] in disadvantages, which is an insanely high amount. The "Cheese" isn't in what what a [180] point mage can do (which is an issue of its own), but building that ruthlessly min-maxed of a character. Or in an arithmetic error.

Now, you could drop 5 IQ and still have all of your questions. So I'll do my best to answer those for the case of the IQ 15 + Magery 3 wizard (which is actually better known).

The wizard becomes useful in the face of anti-magic zones. This isn't for every game, but Dungeon Fantasy suggests using them reasonably frequently.

Your Wizard is versatile, but he can burn through his FP very quickly. He's only got a -1 to cost when casting spells, which is good for whipping out lots of low cost spells, but he can't pull off more than one or two big spells. By way of example, Missile Shield is often given as a fight ender for ranged combat with a wizard. of course, he spends 4 FP to cast it, and only has 2 FP left before he starts taking penalties. Which lets me charge in and try to engage him directly. He's still very squishy.

Out-thieving the thief is a particular problem, and yes, its a known one. Just remember to track FP. And thief characters are usually better risk takers than wizards. And for best effects, the Wizard buffs thief into being a super thief, not himself. Though I was once fond of a combo character who was a little of both, and specialized in such spells.

Your Wizard lacks range. Most spells take -1 per yard. The ones that don't require DX to use properly. Reverse missiles or missile shield can help with that, but it doesn't fix it completely, and it burns through your FP.