Nicely written and illustrated. Will you publish a downloadable complete version when it is complete?
Glad to see that you incuded banked turns. Too many pilots do lazy left stick only turns. Just as in full sized aircraft, banking balances the aircraft making smoother and tighter turns possible, without side-slipping.
You may have already included these comments in parts 3 and 4, but if not . . .
Something to add to your BOX flight, facing the direction of flight. Start on the ground in front of you, rising at 45 degrees to the first corner. After reaching the fourth corner, descend at 45 degrees to the start point. Easy to misjudge the angle. Good practice for combining forward speed and altitude.
Another excercise for orientation when far away, especially if you lose FPV picture, is to spin the aircraft, then work out the orientation. (no cheating by using the Go app!). Then fly towards yourself.
Refine your flight home by trying to keep the aircraft at the same point in the sky, but appearing to grow large as it comes towards you. You will have to balance yaw, descent, L/R and speed. (one technique I used to keep it on track when flying towards yourself, before it became instinctive, was - if the aircraft goes to the right 'push' it to the left with the left stick and 'push' to the right if it drifts to the left)