Oh, and is Danielle pregnant with Alex before she meets Ben? Could he have been telling the truth to that badass army dude who shot her when he said they were not related? If this was true, why did Ben vow vengance on Penny to Whidmore?
I think Danielle had to be pregnant before getting to the island, no woman who has gotten pregnant on the island has survived, which is why it was so important to get Sun off the island. Ben definitely stole Alex from Danielle, and was telling the truth that she was of no relation. But when you raise a baby you form a bond so he loved Alex despite no actual blood relation. The line to the Marine was to try to get him to let her go.
I assumed the time jumps were moving in the same direction (forward), as the last 2 jumps were both at the time where they had already landed on the island (claire's baby being born and the camp existing on the beach).
They jump back forth and all over. Locke saw the plane crash got shot be Ethan, Jump forward to Richard saving him and giving him the magic time loop compass, jump back to before the plane even crashed, so I assumed that after they were there on hatch night they jumped somewhere in the future (camp was there) but new boats and then jumped back to when Danielle landed on the Island... and they'll jump randomly forward and back a few times next episode as well...