This was such a thought-provoking story for me. I love AU fics and I've always wanted to read a non-magic student/teacher Snarry fic so I was very excited when I read your summary.
For whatever reason, I didn't find it to be just another typical light, fluffy, happily-ever-after Snarry. There were times when I actually was afraid of Harry and what he might actually do to keep Severus. His possessiveness scared me and I found his crude attempts at flirtation very uncomfortable. I wasn't surprised that a man like Severus could be seduced, but here there seems to be such a role reversal - Severus as the foolish, reckless Gryffindor and Harry as the manipulative Slytherin.
I found the characterizations chilling, but impossible to put aside. Perhaps I'm reading more into the story than you intended, but I certainly don't see this ending well for either man. I can see from the comments that I'm in the minority so perhaps I'm seeing something that isn't there. But the fic reads very dark to me and, like Severus, I'm waiting for the inevitable discovery and the consequences for their actions. I don't think it will be pretty.
Brilliant work. Realistic and believable. Nice job!