The trope of Jack's character is that he's already 14 steps ahead of everyone else. Trouble is that sometimes you can't rely on everyone to trust you to know what you're doing.
In the cave, when Will and Jack are going to save Elizabeth:
Jack: "Have I ever given you reason not to trust me? Please; stay here, and try not to do anything... stupid."
And then later, after Barbossa's crew capture Jack and his crew, blow up the Dauntless and Will appears, to rescue Elizabeth (again).
Barbossa: You've only got one shot, and we can't die.
Jack: Don't do anything stupid!
Will: You can't, I can! [He points the gun at himself]
Jack: [Defeated] Like that...
There are obviously many more steps to Jack's plan. He has no intention of telling Barbossa who he needs; only that Jack knows who he needs - his goal is not to sacrifice Will, but use him to get his revenge on Barbossa.
Throughout the movie, it appears that Jack is a bit of a loon, doesn't know what he's doing, has no control or is just plain lucky. But at the end, after Jack and Barbossa's sword fight it all becomes clear - the only thing he wants is revenge against Barbossa, after the mutiny he pulled, and stealing the Pearl from him.
No, Jack isn't perfect - in fact he's quite a narcissist. But ultimately he wouldn't kill anyone (or give them away to be killed) if he has, or can see a future use for them.