I disagree that he needed to hate Harry; I can see Harry understanding his life, but loathing a helpless child and inflicting vengeance on them is still beyond the pale. (And there's also the fact that he tormented other children, so I don't think that he only does it because of James). That's one of the reasons that this revelation is going to come as such a shock to him.

I do agree that he's a tormented character and one it's very easy to misunderstand.

Harry would probably be hesitant if someone else turned out to be his father, but not run in absolute fear the way he's doing from Snape.

Yes, the curse is on the Prince line- which is why Harry can't discover it when he tries- but at this point, he has no idea that Snape is anything but a pure-blood.

Draco is trying to grow up now. :)