i still see stewie as ENTJ.
"evil" entp's often just want to see the world burn...they want to stick a big middle finger to the "systems" they are wrecking/manipulating (ie: the joker/any socially manipulative ENTP)
Stewie seems to be more goal oriented...the fact that he never achieves them/is goofy seems irrelevant to me. ENTJs can be creative as well. I would say they often have a conflict in a desire: creativity (Ni), order (Te)...stewie just seems a bit more on the creative side.