I am not a pro or super analytical about these things but watching the video there was something that just didn't look right. Seeing the stills, it is what you guys are referring to as the "backscratch position". The point at which this occurs should be when your right hand (for righties) is very near your ear. I don't see this in either picture. In the second picture, it looks like the racquet should be closer to hitting the ball based on body and arm position. Leads me to believe that there is a timing issue that results in a serve that is mostly all arm.
Also, that does not look like a continental grip. If you think it is, I would suggest moving to what you think an eastern grip would be.
I would guess that you have some athletic skills in other sports since you said you only recently started working on serve. It looks good and you should be able to continue to improve it because you have the basic motion down.