Okay, I admit to going both 'huh?' and 'argh!' at the ending, which was too abrupt and much too inconclusive for my tastes, but right up to that point I quite liked the story.
You do a good job from the beginning with showing how Harry gradually becomes more an more alienated from his friends, who more than anything want to move on with their lives, to shove the past to a safe distance, while Harry, tugged at by the Life Debt and his own sense of guilt over Snape, simply can't. I do like Hermione's idea of a monument, but even that is a way of compartmentalizing, of roping off what's happened, of rendering it somehow easier to deal with, and that's not a bad thing--it's probably even necessary--but it clearly emphasizes Harry's 'stuckness'. I am especially intrigued by the idea of the Life Debt as a tangible connection, with very real physical as well as magical and psychological effects, and I'd like to have seen that explored in more detail.
I enjoyed your characterizations of everyone, from Harry and Snape down to Teddy and Kingsley; I just wish the whole thing hadn't cut off so suddenly.