LPS…
Ok, this is why the movie was too long and should have been split into a 4 part series instead of a trilogy.
Now, remove all the accents and clutter and watch the deleted scene(which explains the last 2 movies) and you get it to boil down to this:
Tia Dalma = Calypso
Calypso promised Davy Jones she'd be there after the 10 years of ferrying souls.
She wasn't.
This caused Davy Jones to be put into service forever, and he ripped out his heart and placed it in a box.
If Calypso were there when he returned, he wouldn't have mutated into a sea thing with an octopus head and been free of the job.
So, without his love waiting for a decade, he'd be forced to continue the job for all eternity.
Plus she was pregnant somehow.
So technically, after 10 years, he is a free man.
Seriously, they screwed the sequels up.