first i'd just like to say it is very difficulty to try to coach someone using a video. second i would like to say as a coach, i generally try to work on one issue at a time in order of priority relative to building up to good shots. after watching the video once, i would say my initial thoughts would be these: you are right handed, and the follow through on your serve comes down on your right side, looks as though this may be an attempt to generate spin. this motion will prevent you from getting the drive your looking for. next, most of the tosses seem to be to close to you and not far enough into the court, this may not only make the shot weak, but may cause it to land long. this toss is also not meant for the kind of serve you are attempting. in my experience the more directly overhead or behind the head, the deeper the knee bend has to be, which you also lack. that is not yet a problem for you since these are not the types of serves youre throwing.
also your timing is off in a way that almost makes it look like you are chasing the ball into the air. i often get players that try to actually hit the ball while it is still on the rise. so until you improve i would say to shorten the toss and catch the ball at the apex of the toss where it stands still, make your follow through come down on your left side, and toss the ball a touch further into the court. now, your serve motion is not as fluid as it should be. you dont seem to allow the racket to stop once the motion has started which is a big positive, since stopping the racket means you have to restart it, which keeps you from conserving or redirecting momentum. so i would say to shadow the serve motion at least 100 times per day at half speed, making sure the motion is proper and fluid. hope thats a good start. tough to try to fix things this way.