Jack betraying Will...
I was thinking about the fact that Jack supposedly betrays Will in movie two, and there is no way we can continue to look at it that way.
At this point in the film, Jack had more information than anyone else (as usual).
He had already met up with Bootstrap- he knew Bootstrap was alive. He also knew that Will was interested in his father, as Will was obsessed with him in movie 1. Jack knew Bootstrap was aboard the Dutchman. Part of his plan PROBABLY involved them being reunited, though under adverse circumstances for a few days.
This also may have been to win Bootstrap's help... Jack and him appeared to be friends, and perhaps Jack wanted to prove to his old friend that his life wasn't completely meaningless by introducing him to his grown up son.
Jack also proves with this that he TRUSTED Will to some degree- because he knew Will had a shot of getting the key, whereas Jones was too suspicious of JACK for him to try for it.
PLUS, Jack had a plan to save him, anyways. He had no real intention of harvesting 100 souls, that was just a back-up plan until he found someone who could use the compass to find the chest. Because with the chest, he could bargain for Will back and for Davy to call the beast off him. If they also had the key at this point, so much the better. He wasn't just going to leave Will on that boat forever. He probably would have included Boostrap in the bargain.
All this to say, there has been a lot of talk like, Oh I cant believe Jack would do that to Will, Liz was punishing him, etc.... and none of that really matches what was actually going on! 🙂
Jack has a true honest streak (which was mentioned a lot more frequently in the original script we just found) and even though he pokes fun at Will, he obviously would risk quite a bit (though not everything) for him...