Extend a line down the arrow and out to the string elbow. See how far outside the arrow line his elbow is?? In the video, he starts with that elbow outside the arrow line and it stays there all the way through the shot. Without seeing in person, that looks to me to be a draw only using the biceps -- No back muscles at all. He is trying to draw in a straight line with the arrow pointing at the target. You can see too how much tension there is in his forearm. He needs to relax that forearm AND biceps in order for a back tension draw to occur.
He's also pretty "hunched" over which isn't helping either.
Arne