First, shouldn't his hitdice be 34d12+306 plus the hitdice(15d4) and bonus for him having 15 levels of Sorcerer(Con Mod * 15)? Also, wouldn't that increase his saves, skill points, and a few other things I'm sure I'm not thinking about. I'd have to check saves and the like, but I'm sure those should probably be readjusted.
I think he should have one more feat. He's got 11 listed and should have 12 I think (1,3,6,9,12,15,18,21,24,27,30,33). That is not including the extra feats he would get from his Sorcerer levels.
He should know a lot more spells. You've only got 3 first level spells listed and he should know 6. He should know 6 of every level up to 6 and 4 seventh.
What is his Quicken spell-like ability?
What is his weapon focus? Wouldn't Improved Natural weaponry be better maybe? Would he want the extra bonus to hit or improving his damage?
NOTE: OK, I'm wondering if it maybe got a little confusing. An ancient Red can cast spells like a 15th level Sorcerer, so I was actually assuming you tacked on 15 MORE levels of Sorcerer to it. Does he have 15 more levels of Sorcerer, in which case he needs a lot of adjusting or does he just have 15 levels of Sorcerer from Red Dragon, in which case you should probably remove that from the Stat block.
If you want, I could probably tonight or tomorrow get around to restating him, or at least making suggestions.