I liked Jacob's line where he mentioned that it took a very long time to make the "thread".
I took that to be an extension of the metaphor that Daniel had made about time being a "string". And notice that the man-in-black is searching for his own "loop" hole. Again, a reference to thread.
So, I see it somewhere along the lines of Jacob being the weaver of the string of time. At least, on the island. Which would explain his tapestry having images of the entire saga. To which, he is aware of how it all plays out, and how time needs to be manipulated so that the outcome is what it needs to be. So, to him, he can go forward or backward as much as he wants. The difference appears to be that he can't do anything about changing time himself, only recruit people throughout time to do it for him.