I am not sure exactly what is going on in the video here.. (don't mind me). It looks like you are just trying to lure him into backing up.. maybe just get him to back on verbal cue?
When I taught a horse to back it was usually quite a bit into his riding carreer and after the horse was more balanced and able to shift his weight to the rear on cue. The horse was doing turns on the forehand.
When I first asked for a back up, the horse would have a barrier in front of him (the arena wall worked well as did a good fence). I would then ask the horse to collect (standing there) and put slightly more pressure on his mouth.. holding the horse with my legs. Most horses will collect and then take a tentative step back.. at which point ALL pressure stopped.
Doing it this way I had a horse that understood the cues to back but also would be balanced and collected backing up. We called in a Reinback in the cenzoic when I was doing this and it was a fairly advanced move.
I am not sure if you want all that training your horse.. maybe all you want is the horse to walk backward on cue and not have him collected and able to take a right angle turn etc. like some trail classes require.
IOW's I am not saying what you are doing is wrong.. just what I did and how and why I did it taht way..