I think that for Harry a large part of the issue is that he would always be second place for Severus and, given his past, that's a bitter pill to swallow. In retrospect, with effort and hard work, I suppose both could overcome their personal issues and reconcile as better, stronger people, but Harry doesn't see any real need to change his expectations and Severus is very much mired in the past. Moving forward is too daunting a task for him in many ways. Besides, Harry is too sure that he's 'right' in this situation and Severus--for all his posturing and arrogance--always seems to be willing to take the blame for things. He's very invested in his suffering.
Thank you for reviewing, and I'm really glad you enjoyed the story. :-)