Voldemort use the AK curse because on p. 743 it says that Harry saw Voldemort’s green jet meet his own spell, saw the Elder Wand fly high..... the AK curse is always described as a green jet in every instance that it is used. Also Voldemort had the Elder Wand but the actual power of the wand was in Draco’s wand, it transferred it’s power to Draco’s when Draco sent Dumbledore’s wand flying. The power is what made the wand not the actual wand. That is why the Dumbledore’s wand was buried with him and didn’t do Voldemort any good, it had Draco’s wand’s power. This is JMO> :)
But the spoilers aren't gonna spoint my reading.
(Alright! I peeked!)
Thank you! I guess I missed that part in my haste to read what happened next.