Who was in the cabin by Sawya

I've been reading some interesting theories and I'd like to remark the one that says that Flocke is not able to change his appearence because the cabin has been destroyed.

That's a really interesting theory: Ilana knew that he couldn't change his image any more. Why? Because she was the one who ordered to burn the cabin. That would mean that the cabin is some type of "changing room" which, I think, Jacob used to change himself: asuming this, the Christian Shepard that we have seen off the Island was Jacob (because MIB is not able to leave the Island). In the hospital, Jacob was trying to bring back Jack. Maybe, when he appeared in Widmore's boat, maybe, he had not time to change himself and had to appear with that form to Michael (I know that doesn't make much sense but... I can't imagine anything better).

So, according to this, the Cabin was the place where Jacob changed his image, and the circle of ash impeded MIB to enter so he could not change his body and cheat anybody. But the circle of ash got broken, so MIB was able to enter and adopt new forms. That's when we see Christian Shepard on Island, the one who conduces Jack to the caves and the one who tells Locke to move the Island, etc.

If that's true, the one who says "help me" to Locke would be MIB, because it's him and not Jacob the one who needs help.

But Hurley finds the Cabin and looks through the window. He sees two persons: Christian Shepard and someone's eye. I think that those persons were Jacob and MIB, who probably were having another deep talk of those that they use to have when they meet. In my opinion, the eye seems like MIB's, but that's not sure at all, because if they were both in the Cabin (asuming that it's a changin room) they could both look like anybody.

But if Jacob knew that MIB could enter in the cabin, why didn't he put another circle of ash, as the first one got broken? Maybe there's a rule that doesn't allow him to do it, or maybe because that's the point in which he realizes that MIB has found his loophole and decides to let him finish his plan.

Resuming:
The cabin is a changing room, probably using that extranges substances which are there. Jacob used it to manipulate the Candidates' life (appearing to Jack as his father, for example) until one day in which the circle of ash got broken and MIB was able to enter there, and change his form.