I'll see if I can help...
Beckett and Jack:
Beckett wants to know what the pirates are up to, and he wants Jack to give him information. Jack instead offers to lead Beckett to Shipwreck Cove, and then he promises that he will lead the pirates out of the 'fortress' so that Beckett can destroy them.
Jack, meanwhile, gets the Pearl, his debt to Davy Jones is ended, and he chooses his crew (Cotton, Marty, Elizabeth, and Gibbs), and tells Beckett that he can 'have' Pintel, Ragetti, Barbossa and Will.
Barbossa, Liz, Will and Sao:
Up on deck, Will is peeved to discover that Sao sold him out to Beckett, and that Beckett is taking the Pearl. Barbossa is trying to convince Sao to come to the Brethren meeting, and he leads Sao to believe that Elizabeth is Calypso in disguise, so Sao agrees to go to Shipwreck Cove -- as long as he can have Elizabeth.
Elizabeth and Barbossa agree, and they begin to fight Beckett's men.
Jack Calls Will a Traitor:
Well, yeah. Will led a mutiny against Jack to take control of the Black Pearl. 😄
Will won't die when a new captain is chosen. His heart is beating in the 'Dead Man's Chest', so he's alive. Technically. 😉 When the ten years are up, Will is released to the living world (hence the green flash at the very, very end of the movie).