Please don't apologize for the "essay", I love seeing the feedback that stories like this generate and I appreciate you sharing your thoughts.
I think you make some good points. I disagree that Jack didn't have a choice. His choices were shitty yes, but he made them and had to face the consequences. One of them was a former friend who desired revenge for being abandoned when he was most vulnerable. Damon also had to make some choices, and his were shitty as well. He could have chosen to leave Jack behind and enjoy his new life with Will, and he didn't.
Everyone made bad choices here. I wanted a story about revenge, because I'm just mean like that sometimes. It's up to you to decide who is redeemable. I'm glad this was able to inspire an idea for you.