Oh, did I mention Padma and Parvati?
He should also do Pansy as a punishment both of her and Draco. Turn her into a sort of power vacuum; she can go fuck all the Slytherins, taking their power, and then come back and give that to Harry.
Keep Ginny. Those who read her as giving her a potion are off their rockers. Plenty of people saw her paired with Harry long in advance (so no on can say there's no evidence of the pairing; even if there isn't, so what?) -- there's more evidence of Harry with Ginny than with anyone else in canon.