i think that the others took jack so he could operate on ben, kate and sawyer are the bargaining power
that guy wants to shoot sawyer as revenge for sun shooting and killing his wife
the big cliff hanger will end in the next episode by kate telling jack there's no point her running as there's no where to go. jack doesn't know they are on a different island yet but kate and sawyer do
i get the feeling that the writers are making it up as they go along now but am still hooked nevertheless