This is way too skillfully written to have but one review, so I take it upon myself to ad at least one more.

Fantastically depressing, my love! I'm sure that was your intention, and you nailed it.

Can't give much constructive critisism, since I'm not a fan of HP and don't have crystal-clear and definitive imagies in my mind of how the characters are, so I have no points of view on your chosen perspective and the motivations and psykological profiles you've given them. But I CAN say that you probably have a powerful story going here, and you should pursue it.

Wow! I'm impressed! I can't wait for the next chapter!