Ballinbob, my level of play is not high but I will share with you what a couch has been pushing me to do. Very good information on this thread, by the way.
Anyway, I will mention the parts that I think applies to you.
1) Push forward when hitting the ball. Your arms goes forward by your body doesn't (on most of your FH shots). This also takes time away from you to go to the net since your momentum is pushing you back.
2) 3:13 Plant your opposite foot/leg on the front. Pros hit open stance but only because they don't have much time and copying them is a mistake. I practiced my open stance I guess too much that I was hitting 9 out of 10 balls open stance when I had plenty of time to use a closer one. Myself, I'm now closing it more and use my open stance when I don't have much time. It give me MORE dept and pace.
3) 3:13 Don't let your opposite leg be in the air at the moment of impact. I got used to it and I was hitting (ok still) hitting like that too much. That is suppose to be an out of trouble (not enough time) shot and not part of my common shot. I think you are doing the same.
4) Don't cross your right leg too much behind you because it will mess up your balance, let you lose high consciousness of where you are with the net and it's just a bad habit. My couch says I should wear a tutu, if I want to be spinning too much. It make me lose power.
4) Use your hips and shoulders more.
5) You are opening your shoulders too quickly, in many occasions. A good example is at 1:22, on that one it also dropped. On your earlier videos that was more noticeable, however.
I'm working myself on the above. My problem is that my left knee is bad and huts so I'm been compensating, while modifying my game (learning bad habits). My knee has been feeling better for the past 1.5 months so I'm ready to work on fixing my problems. Gotta a new racket, new strings and I'm ready to go. I have also just started changing my physical habits (workout outside of tennis and take some supplements to help my body recover).
Anyway, good luck and again, good info here.