Ok, I'll take a shot at this:
Why? How? Sorcerers are spontaneous casters. It kind of makes sense to have a spontaneous caster in a spontaneous spell system.
2) Spell aquisition, scribing & learning as per normal rules.
This I have never agreed with. Two spells per level is ridiculous. Instead, maybe try 1 new spell per caster level at each new level: a 2nd level wizard advancing to 3rd level gets three new spells, a 3rd level wizard advancing to 4th level gets four new spells, etc.
Scribing rules are ludicrous. 100gp per page?! At 100gp per page and 100 pages per book, that's 10,000gp to fill one book and for what? One page per spell level of the spell. That's a pitiful amount of spells available for 10,000gp! And what? So the wizard can study out of it? Big deal! That's nothing more than an excuse to get the wizard to part with his gold, which would be better spent on creating items. Wizard asks the group, "Well, guys, I can copy these nifty new spells into my spellbooks or make us all Rings of Protection +2, but I don't have money for both!" Guess what the party will have that wizard doing? Just how special does that quill have to be, or the ink or the paper, to write down something the wizard has to memorize? He memorizes what he sees, not the ink or paper it is written on. The words he studies would look no different if written with 2cp ink vs. 100gp ink--maybe prettier is all, or in different colors.
Learning new spells rule is fine.
3) Caster level check to cast spells = DC 15 + spell level (1-9).
Not too bad of an idea. Casting should never be perfect just as warrior-types never
always hit when swinging their weapons. Granted, wizards get fewer spells than warriors get swings with their weapons, but it should still not be automatic. It should may be a skill. Otherwise, a 15th level wizard would cast any 7th level or lower spell on a 7 or higher and would only fail a 1st level spell on a 1. That said, I don't see too many 15th level wizards goofing up a Magic Missile.
4) 1 threatens a fumble, int check dc 20 avoid.
6) 20 threatens a critical success, int check dc 20 confirm.
I put these items together for the same reason: Why? How do you fumble a Detect Magic? Just how much of a difference is a critical success? A 10th level wizard casting a Fireball at 12th level still only does 10D6 damage. If you're doing it to compare spells to weapons, weapons have different critical threat ranges. Why wouldn't spells, if you were going to adopt this feature? And considering that weapons can inflict double, triple or even quadruple damage (and often more than any spell would do), a critical success on a spell (+2 caster level) doesn't even compare to that.
Also, instead of an Int check to avoid, why not make it a Concentration check? That's what the skill is for. And if you're doing it to compare spells to weapons, then there should be no confirm/avoid option. Fighters don't have the chance to avoid a fumble. Why should a wizard? If he's thinking of sipping tea and a nice warm nap while Gating in a Pit Fiend instead of paying attention, he should 'fumble'.
5) Fumble fails to cast & confers -1 to caster level check until rested.
This one alone is reason enough not to play a wizard in your game. What fighter suffers a -1 for missing an attack roll and for the rest of the day. Yeah, the fighter could be incredibly embarrassed for slipping and dropping his sword or tripping and falling on his face, but he won't beat himself up about it so much to self-induce a -1 penalty to hit until he rests and perhaps feels better about himself in the morning. Why then, should a 10th level Wizard, fumbling his Mage Armor spell, have to suffer the rest of the day!
If you want him to flub the spell, that's fine, but that should be it. Wizards have a limited number of spells already, and the effectiveness of those spells is already challenged by counterspelling, spell turning, spell resistance and other powers or abilities or other spells. If you absolutely have to penalize him further, then just add 2 to the DC check of his next spell he casts in the next round or two. That should be sufficient. After that, he should be calm and collected (and recovered) enough to cast without further penalty.
8) when current caster level = 0, lose casting ability until rested
About the only time this happens is with Energy Drain, by spell or ability. And then, even if a Restoration or whatever is handy, no spells are returned until the caster rests and studies again. So, this is kind of already 'in the rules'.
9) The maximum number of spells known is 10+int bonus for each spell level.
What is the purpose of this restriction? A wizard can only 'know' so many spells of each level, and then of those he 'knows' he can only memorize up to 6 or so at a time anyway? So he has to essentially learn a spell twice (knowing it and memorizing it later), forgets it once (as soon as it is cast) and then has to relearn it yet again to cast it another time. That is silly. So what if a wizard 'knows 15 or 20 1st or even 5th level spells (or any other level for that matter)? As mentioned before, he can only prepare maybe six or so of those 15 or 20 spells in any given day. This just places yet another needless, and unjustifiable, restriction on wizards that serves absolutely no purpose beyond reducing their versatility. If you do this, consider limiting fighters (and any other non-wizards) to maybe 10 weapons + 1 weapon per point of Intelligence bonus that they know how to use!