From serve video now in the OP.
I look at videos and point out what I think might be differences from most better high level serves. You should compare these points for yourself using high speed videos from similar camera angles.
Frame #1. The upper arm of your hitting arm is high compared to most stronger ATP servers, where the hitting upper arm is down more in line with a line between the two shoulders. There was a long thread on this issue for Vladisova's serve. See also Ellenbecker video on the shoulder and upper arm positioning on the serve.
http://tt.tennis-warehouse.com/inde...-high-elbow-in-her-serve.513485/#post-8756768
Look at the tossing side of your body and the hitting side of your body and compare to those of high level servers. In other words, compare the so-called 'hip thrust' or 'archer's bow' bend for you and high level servers. I don't know how much variation might exist among high level servers on these issues. Take care bending your body.
Frame #2. This is where your legs first thrust upward. The forearm and racket are tipped back more than what I've seen in my small sample of better high level servers. High levels servers who move continuously through Trophy Position sometimes start their leg thrust when the forearm and racket are still tipped
forward - different than you. This positioning and timing may also depend on how much the chest is pointed upward. ? Actually, your forearm and racket position when the legs first thrust seems reasonable to me so it may be an option. ? ...study forearm and racket position when the legs first thrust upward.
Frame #3. This is the racket
edge-on to the ball checkpoint that we mention for evaluating serves (if the racket were
face-on at this point then the serve is likely a Waiter's Tray). Looks like good edge-on.
Frame #4. Just before impact. If you view the video from Frame #3 to Frame #4 you can see that the racket goes from
edge on to
face on to the ball because the wrist rotates with the arm. Wrist rotation in turn is caused mostly by
internal shoulder rotation (ISR) of the upper arm with some
pronation of the forearm also. ISR rotation, according to researchers B. Elliott et al, is estimated to contribute 40% to racket head speed at impact. This part of your serve looks good as far as I can tell. You would need better high speed video to analyze it in more detail.
Frame #5. Foot landing. Go back to Frame #2 and look at the starting point for the foot. Look at how far the foot moved between Frame #2 and Frame #5. That is not much total forward motion for the foot. Compare the forward motions of your serve to high level servers. There is a lot of variety in forward motion among servers. Raonic, a good serving model, moves forward more than most. Related to forward motion is the posture at impact as seen from the side, the trunk and arm are tilted forward and the racket is upright (as seen from the side) - see Frame #4. Some servers move forward much less than Raonic. Compare your forward motions - head, impact, landing foot - to a number of better servers and see where you fit in. Are you tossing and moving forward enough?