>whole bunch
that's basically the only two you'll be able to emulate with 5 lvls of factotum, and you can't do it "whenever you want" since you have a limited number of inspiration points/encounter which is far lower than the amount of spell slots a wizard (or cleric/sorcerer/druid/etc) has for each encounter.
sneak attack is pretty worthless on an absolute scale and factota don't get enough of it to autowin any encounters. their opportunistic piety is also just atrocious for turning undead since your ECL is so low. it's not like he's going to be able to make your rogue or cleric feel useless, he's just not good enough in either sphere to overshadow anyone.
and again, casters can already do stuff like that via wracking touch or rebuking breath, to such a degree that it actually does overshadow classes that are good at stuff.
anyway, you'll see for yourself when gametime comes. I strongly encourage you to allow factotum. they play exactly like a rogue if rogue didn't suck so hard.
if you're skeptical, stat one up and try it out in some quick pregen encounters. you'll see he won't overshadow anybody.