I like it. Good technique (good shoulder turn and tilt), good power, good kick. However, your toss seems a bit out of control, and, you seem to be trying to muscle the ball with your arm too much. Slow it down from the beginning of your motion, including your tossing motion, and stay totally loose and relaxed all the way through. Start your motion slowly and gradually accelerate through contact. That little step you are taking with your front foot also makes your toss a little more of a challenge to place correctly.
What I didn't see, though, was much demonstration of your ability to locate the ball where you want it. IMO, location and deception are more important than power and kick. For deception, I try to toss and set up exactly the same way no matter what kind of serve I hit, or where I hit it. I vary my serve (ie: slice, kick, hybrid), by how I position myself under the ball, and I vary my location by how soon I come out of my turn. Most opponents don't know what's coming, or where it's going until after I hit the ball. That's a huge advantage.
For your shoulder, I would highly recommend two things (speaking from personal experience): (1) rotator cuff specific exercises daily for as long as you play tennis, and (2) ice for 20 minutes after every practice for at least 3 months, Advil as needed from there on out, assuming you can tolerate Advil. Start now, while you're young. You will regret, sooner or later, it if you don't.
You can do a Google search to understand what the rotator cuff is, and what discrete exercises you should be doing. The 4 rotator cuff muscles and tendons stabilize the joint (keep the ball in the socket), they don't move your arm. The exercises you need to do are very specific and are meant to strengthen the rotator cuff muscles, not the skeletal muscles.
The 3 exercises that helped me the most were: vertical rotation, internal rotation and external rotation. I use an 9lb dumbell for the vertical rotation, and a "Thera-band" exercise band for the internal/external rotation exercises.
Hope that helps.