Arrow length usually doesn't matter, but I suspect there's a little more to consider in your situation.
I can't tell from the angle in the video, but it doesn't appear that you're getting full extension. Looks to me like your holding at full draw with your bicep rather than your back.
If you'd have someone get above and behind you (from a step ladder maybe) and film another video we could tell for sure.
*Refer to the diagram at the top of the page.
Again... you're doing GREAT!