^^^No,....I agree with Willo on that one.....Jack's look of horror is that he sees Will is stabbed and Liz's pain....if the only reason Jack is upset is because his planned is screwed up..then that would make Jack pretty much a cold hearted ba$#%$d!
Jack is a good man...he has a good heart...too good to be a true black hearted pirate....that's why Jack's plans never go as planned....as Barbossa told him "it's exactly that kind of thinking that did you in the first time Jack"...and notice that's what Captain Sparrow tells his good side in purgatory...."it's exactly that kind of thinking that got us into this mess in the first place"......
I truly think Jack's look of horror is that he realized he hesitated in playing with Davy and didn't stab the heart quick enough and is horrorified in that Will has been stabbed in the heart and Liz is screaming and hysterical....despite everything, Jack cares about those two kids.....
I think Jack plays around with Will and uses him because he thinks Will is easy to manipulate....but I think he cares about Will, truly I do.....because of Bootstrap.....think back to COTBP when Jack describes Will's father to him...Jack kind of had a father worship in a way for Will's father himself......