You'll notice I edited my post - which took longer than I intended, thanks to a phone call - and didn't see your post until I submitted it.
With the current requirements and skill points, it's not unreasonable. Skill Focus and Combat Casting are the only real feat taxes to enter, but entry requirements are much more challenging, now. I don't see why you're requiring level 4 spells, though.
3 Fighter/5 Wizard has 3rd spells, all the feats (plus three or four more), and all the skills (plus two or three more). If you require 4th level spells, you prevent a multiclassed character from having more than 5 levels pre-epic. Is this as intended?
Edit, starting 9:03EST:
I still have trouble seeing how this isn't awesome near-free stuff for a pure wizard, though. Skill Focus and Combat Casting hurt to spend (because neither is a very good choice in NWN, unless you're Casting Defensively all the time... In which case they DON'T hurt to spend), but Dodge and Mobility aren't bad at all. MWP is great. A combat-focused Wizard would have no problem paying all of that for a Full BAB (and therefore another attack per round and +5 BAB by level 20).
Another thing to consider is that you're designing a PrC basically JUST for wizards. We've got a couple of those already. Do we really need more?