There must be a reason why the man in black hasn't been named yet. In my mind, the reason is that he is one of the characters we already know and so revealing this too early would spoil the surprise that is to come. I believe his name to be Aaron, as this would back up the statement of the psychic that Claire saw, claiming that he should not be raised by anyone but herself. It would also be typical Kate to meddle and get in the way, this time with consequences completely out of proportion.
Juliet's last thoughts were "it worked." She mumbled similar incoherent ramblings to characters disorientated by the time flashes such as Mincowski and Charlotte. She has seen into the other timeline, where she and Sawyer are having coffee. Does this suggest a happy ending? Certainly for Juliet and Sawyer, who I believe will live.
I also believe the numbers to have no significance whatsoever. What common ground could stand between winning lottery numbers, a serial number on the hatch and the code to maintain a pocket of electromagnetism? LOST relies on coincidence here, although this would be a huge letdown.