Based upon what the DM says I'd then begin building the character. Does anyone have any suggestions, tips, and tricks regarding this class and PrC combination? If I understand it correctly the Factotum is pretty much a god when it comes to skill checks and the like... and his ability to access spells from the Wizard's spell list makes him insanely versatile. Then with the Chameleon's ability to have that floating feat selection. Insanity could easily ensue.
My only suggestions for actual play are from my experience in my gestalt E6 game, so it may not be relevant at your higher level:
First, leave at least 1 Inspiration Point in your pool at all times. Then, when you have to make that save, you can spend the point to add Int to a save.(in my character's case practically guaranteeing I make it on anything but a 1) This tactic has saved my bacon more than I can say.
Second, adding Int to damage is determined after you successfully hit. My fellow player/dms like to roll both their damage dice and the d20 at the same time. I cannot do this. Also, if I spend inspiration on damage, I never feel as though it was wasted inspiration. This is probably not the case at higher levels however.
Third, expect your DM to make a reasonable houserule regarding the number of times you can use cunning surge in a single round. Don't just surprise him with cunning surge either, be sure to ask his opinion on the matter before
you begin playing. If you can surge only limited by your inspiration points, then by all means, take Font for all of your feats. If not, just take it 3-4 times like everyone else suggests.
Also, it's too bad you can't snag Magic of Incarnum as an extra book. Incarnum feats + floating feat = win.