So here's why I don't think Jacob is really dead:
During Sawyer's FST the dad from LHOTP told his daughter something along the lines of "you're not really gone once you die" (not exact quote).
Everytime Hurley sees Jacob he (Hurley) is by himself, which means that Jacob may be able to quickly travel around the island much like MIB. And as far as the scene from the LightHouse, Jack was completely pre-occupied staring at the water and didn't look Hurley's way once.
The Ankh symbol Jacob gave to Hurley means "eternal life" in Egyptian.
And finally, are we really supposed to believe that since their existence, that MIB could only con 1 person into killing Jacob for him?