I also like the sound that Jack was 18 when he did whatever he did to Salazar. It means it won't be just a random part of his adult life but a very specific age. Makes you wonder the kind of person he was then and that part of his past that we don't know about is creeping up on him this time.
So far, they'e saying all the right things. I'll take it being like the original with a grain of salt, but all the ideas sound great.
To me, Salazar is just another villain who has a preexisting grudge with Sparrow. Why can't they give us a villain who has no idea who Sparrow is?