That's not even circumstantial evidence, buddy. Your opinion is based on bad detective stories where the killer is always the one you least expect. If Jacob was really involved in some dark deeds, we'd have found clues or hints long ago, but there aren't any.
So far, everything points to Nick. It's a false trail and he's too obvious as a traitor, but there's no better option. He may turn out to be the traitor, because from the looks of it, he's a coward.
The only thing against Jacob is that he wanted to kiss Zoey!