If you follow his hands he certainly looks like he is playing at least the melody line, and in a couple of parts he looks to be playing melody/counter melody with both hands ... if not he is very good at 'finger - synching' ... ...
as for the background vocals, at the end of the video he gives acknowledgement to two female singers ... so perhaps he was playing to a midi with live background singers off to the side ... he does look off to his right on occasion ...
On the flip side, once I see a lap-top nearby, I ALWAYS wonder how much is actually being played ... but then I am sure people wonder the same thing about me when playing my kn6000 ... ...