As a 16 year old, you have a good base to work with. I would recommend three things immediately:
1. Lose the Knee Savers. This should allow you to get lower in your stance. Also along that line...get more flexible in your hip flexors. Take a yoga class. You have a pretty good sized frame and you will need to present a low target at times. Flexibility is very important.
2. Find a long toss or arm strengthening/stabilizing program. We use Jamie Evans' Velo-City (http://www.baseballvelo.com/).
3. Footwork - your feet need to be faster. Jump rope or agility training may help here.
Concur with what Redbird recommends. Would also add some box jumps to help with making your legs more explosive. Your receiving and transfer can use some work as well. Work on after the catch to bring your glove hand straight back to your throwing hand. You have a tendency to catch the ball and push down and then around to your throwing hand. Might want to look into some good catchers training in your area. I know my son belonged to a catching academy (once a month training) that was very beneficial. Good luck!