You're a State fan aren't you. Everything you've addressed are the things floating around State boards as to why he'll bust at UNC.
As far as the State coaching job went, it would've been like UNC downgrading from Bunting had it gone the same. Sendeck wasn't a bad coach. He was doing what he could with what he had at hand and the fans basically drove him away.
As for the Browns gig, Davis was basically asked to step down or be fired. So he was basically let go. Then again he's the only coach to take the Browns to the playoffs in long time.
As far as leaving early, I guess its possible, but then again if UNC is a national power by the time he leaves does it matter? If you're a national power and willing to pay, they could possibly retain him or get another up and coming guy. I think Magnus said it before. If you can get a guy like Davis, you appreciate it for what its for rather than looking at "what ifs".
Then again if you look at State's shitty team this year, and consider what talent Amato has wasted, you've gotta figure they won't even be in competition themselves.