I dont think Jacob has been looking for a candidate to replace him or to protect the island as such, I think the job of the candidate will be to end MIB once and for all, to do the thing that Jacob could not. I think Jacobs role was to keep MIB trapped, because for whatever reason the pair cant kill one another so keeping him maintained was the best he could do. To keep Good and Evil in balance. I think Jacob knew though that there was a way of killing MIB, and Jacob knew one that one day MIB would find a loop to kill him. I think Jacob knew his own death was necessary in order to end MIB. After all Jacob did say that it ends only once, everything up until then is just progress. I think that Jack is the candidate, particularly because evil incarnate has taken the form of Locke, and these two have always been paired off.
I think that Jacob and MIB are representations of Good and Evil. I dont think they’ll have a biblical context, or an ancient eyptian or aztec connotation, I think all the artifacts and enscriptions we see are to remind us that ideas about good and evil have existed throughout human history across many times and cultures. I think this is the writers original take on very ancient ideas about morality and human nature. I think the island might have been home to some kind of great and unearthly power, I mean so far we’ve seen it time travel, we’ve seen a pool that heals people, and I guess soon it’ll reveal why richard doesnt age. I think maybe MIB did used to be a man, and I think him and Jacob came to the island, or perhaps were the original inhabitants of the island. I think maybe there was some place on the island that remained protected because within was some kind of power, some kind of force. Like a Pandoras box of sorts. I think MIB was the first person to let it out, maybe because he lost someone, but for whatever reason his human weakness made him let out some kind of dark force. Maybe like a deal with the devil. And thus maybe he is the source of the darkness that infects others. Maybe he is evil incarnate and his mission is to spread to all people.
I dont know what he means by going home. I think tho that he isnt allowed to harm the candidates. I think tho his plan is to recruit as many people as possible so the scale of the island dips to the dark. I think he wants the candidates dead tho so he can claim them. I think he tried to lead Sawyer to his death on the rope ladder. I reckon it’s only once all the candidates have turned dark that he can go ‘home’. I dont think this is an actual place, i just think this means he’ll have passed the curse on to someone else and he’ll be free of it.
I think the alternative reality will be the way to ensure MIB doesnt win. Not sure how tho! But this is the last season, and I strongly believe that the only way Lost can end is with the Island ending, no loose threads, no what ifs of a follow up, a clean definitive ending for all the characters and island. I think what we are seeing now is Jacobs loop, his way of levelling the playing field once and for all.