4. That's a legitimate bit of personal canon and I can see some of its plausibility but given how little we know about that time, it could just as well be likely that Snape was revelling in the attention he was getting from the DE and Voldemort. He did after all spy on Dumbledore and Trewlawney during the prophecy and went away to tell his master about it, knowing that the logical conclusion would be death for if not the entire family, then certainly the chosen baby. That doesn't really speak to me of a man who's realised it was a mistake and is trying to downplay his helpfulness in the systematic persecution and segregation of muggles.

And well, we probably just have different outlooks but I don't think the crappiness of his childhood particularly absolves him of his actions - our upbringing and growth extends well into our the last stages of our lives, so at that time, teenage/young adult Snape can't hide behind an unhappy household because he's had other experiences in life. I get that people feel sympathy for him but having a reason for being a arsehole doesn't make someone any less of an arsehole in my opinion. Until they acknowledge it and genuinely try to change, that is. Which Snape never did until it was too late to save the girl he loved.