Scott was a dick when you think about it. He did a lot of things out of his own interest with no respect for others around him
What I'm trying to say is that Cera made Scott more, uh, aware-seeming. All the things you said aren't Scott being willfully dickish, he's just a dumbass who doesn't think ahead.
He did fine though, I'm probably just knocking him because he doesn't match the exact Scott I had in my head when I read the comics, but that'd be impossible.
I'm obsessed with the clash at demonhead song. .
You should really consider either downloading or buying the movie's OST then, it's surprisingly awesome.