Lovely! Poor Severus, doing his best to keep Harry safe and then Harry developing a fatal illness he could do nothing about. I think the moment when he had to tell Harry he probably wouldn't be able to do anything was one of the most crushing--Harry clearly believing Severus would be able to develop a cure, regardless what the healer said. And when Harry got the letter back my heart broke a little. That burst of energy, the way they spent that day together--such an emotional roller coaster! As for bitter, old Petunia, I think you got her spot on, including cross-examining Severus about his relationship--not many people can get away with that but as someone that knew him of old, she can. Really nicely done. Great job.