Chris,
It is a little hard to tell for sure in these videos so this is kind of a guess based on an overall shot impression.
It APPEARS that you have the entire draw done with the drawing arm with little to no back involvement. As you draw, the string side shoulder has little to no movement toward your back (away from the camera) and your string elbow appears to move straight back (away from the target).
You might try this as you draw. After lifting the bow (set up/pre-draw) think of moving your string elbow around your spine and not straight back inline with the arrow.
If you can get a fair(if not all) amount of tension out of your arm (especially) the forearm and wrist, you will be forced into using more back muscle. This will (or can) go a long way to reducing or eliminating the hand flip that you have now. Relax the arm and move the elbow around the spine.
Your string side follow through is, right now, an after thought. Something you are DOING not something that HAPPENS.
Arne