As to why most folks can't "see" Jacob or the others. I believe you have to be "receptive" to them. Kinda like Dreyfuess in CE3K. Not eveyone can receive the signals. Walt could, Jack can (sometimes) Locke can, when he's not seething, Desmond... I'm not sure about that "brother".

Benry and "da boys" are doing the TG's bidding, keeping our grubby hands off their stash till they can return or finish up what they want. The folks behind the original DI want the Island in the worst way for either immortality or time travel. Either of which would change the world as we know it. The grubber's planted the fake plane so that they could safely kill off all the inhabitants of the Island and take what they want without "prying eyes" looking for them.

God I've GOT to stop drinking my lunch.

Da Worfster