The first paragraph engaged my interest. It would be something that I would have liked to read in the seventh book, had J. K. Rowling been as descriptive as you are when it came to Severus's death (or at least changed POV's).
The anxiety and anger that Severus felt was heartbreaking. His confusion made so Harry miserable and desperate to make his husband regain his memories. For a moment when they had sex, I thought "problem solved, he's going to remember everything," but he didn't. I thought it was going to be a sad ending...You're clever mystery author, the ending surprised me. You didn't make Severus regain a majority of his memories. Instead, Severus decided that he's going to make new ones with a family that loves him.