Araph, you've got too many skills. I suspect you haven't done your cross-class skills properly; for skills that are not class skills for the class you're taking a level in, each rank costs 2 points. So, your ranks in hide and move silently are both costing you 2 points each, as is your rank in Use Magic Device.
Maelrigar's entire build revolves around maxxing out the amount of armor he can wear without taking an Arcane Failure Chance, buffing himself out with his worse-than-average sorcerer powers, and then using his melee stats and buffs to do some frontlining.
If he were to duel an actual sorcerer... well, I suppose it depends on the sorcerer, and how he does on his saves. At higher levels, he won't be able to do the heavy-duty blasting that sorcerers typically do, but he'll be much better at duelling than most fighters, even with his lack of combat feats.
Also, I'm going to make a ruling about selling spellbooks (which is not going to apply to Finni's already-sold book). Since splatbooks are available, but spellbooks are defined as having "all the 0
th level spells you can cast", from now on, all the level-0 spells take up a total of 20 pages. This counts towards both the price you'll get for selling it, and how many spells you can write into your book.
Maelrigar is a really intense attempt at nerfing a character gone awesome. I mean Shoruke threw a CR 9 spider at us (a little too strong for us) and he dealt the vast majority of the damage and killed it.
CR 6, actually. But still.
Regarding the experience, would it be possible to stagger it somehow?
The experience system in D&D is self-correcting; since you're lower level, you get more experience in every fight. Well, more experience than the people who have hit level 4, at any rate. Characters from level 1-3 are all in the same exp bracket. (seems weird to me, since that's the point of a character's career where being even one level behind hurts the most, but whatever...)