I see one thing clearly different from what I have noticed in videos of top pro players - the height that your racket attains in the backswing is much lower than theirs.
For example, look at racket face height and upper arm height the Heinen's and Federer's backhands.
In these videos the racket is above the head just prior to the downward & forward swing.
In your stroke, the racket is about at your waist height.
In my opinion, there is probably a biomechanical advantage for getting the upper arm (humerus) up
somewhat - it stretches the largest muscle attached to the arm, the lat. Forehand too.....