Who says jacob is the good side? The guys in the temple never said they like jacob, just his guitar cases.He is 100% not Jacob, if he was, the "Others" in the temple wouldnt want to kill him. I think "Possessed" means Sayid is gonna join the dark side, not the Jacob one.
It can still turn out to be something else :P"Man In Black" or Jacob's rival or "The Dark Side"
For the rest, you make good points. I'm thinking mostly the same at everything.