Absolutely intense action-laden story-telling, wow! The imposter accosting Harry was creepy, to say the least. I loved how Harry went by instinct, just knowing that Draco would never wander around without his wand. There are some subtle and awesome things here, about Harry getting to know Draco, like when he realises that Draco lies awake an hour before getting up in the morning to collect his thoughts for the day. It felt so intimate, almost like we should not know that about Draco (it felt like that to me, at least).
As for the two Dracos - splinched-off personality is my guess now. Although the words of impostor!Draco imply some broader plot. But it seems the real Draco is so absurdly clinging to his hatred for Harry, as if he's in fact trying desperately not to fall for him. Thanks for telling this fascinating story!