Even with a starting Int of only 16, you'll be getting at least 7 skill points per level by the time you're done with Factotum 8. When you consider that most skills aren't worth taking beyond 5 ranks (especially with Cunning Knowledge), that should be more than enough to do most everything you'd want. Even some other skills like UMD don't need that many ranks to be brutally effective (especially when splashing Incarnum).
As for what to do with all those levels, Factotum 8/Incarnate 4 gets all the best goodies of your base classes. Beyond that, splash something that makes you better at something else, because skills are covered.