As for the range question.....(im only 17 but this system has been taught to me by a number of people, and I've seen results, with and without my braces)
Basically, the two trumpet players who have worked with me on increasing range, taught me it really lies in understanding how you produce sound on the trumpet, and how you breath. First if you form a buzz (no mouthpiece) and push on your lip with your finger, the sound stops, almost immediately. However, if you push on your bottom lip the sound stops. Secondly if you pull your corners back, your lips thin. Your lips play a huge part in creating a proper sound and tone.
Now putting the two little tid-bits of information you can gather a few basic things, which are quite obvious:
-pushing your horn into your face, unless you are angling it down, pushes on your top lip. you push on your top lip, the sound stops.
-by pulling your corners back, it does work in playing higher, yet it thins out your sound as you continue to go higher
After the little education behind the way we produce sound, they went into the breathing aspect of trumpet playing, and ever since my lesson with the first guy, breathing has become my focus everytime I pick up the horn. The first thing I was told regarding breathing was that if you watch a very young child, when they breathe in, their stomach rises. As they breathe out there stomach lowers. When you yawn, its typically because your body is deprived of oxygen, and as you yawn, your stomach will most likely "rise" as you yawn, and lower as you exhale. This kind of deep breathe, fills your lungs fully, from the bottom to the top, and it is this type of breathe you want to take in everytime you breathe while playing (ideally). On the other side of the spectrum, the average person when they are told to take a deep breathe, if you watch them, will raise their shoulders and their stomachs go in, and on the exhale the reverse happens. When you breathe like this, only the top of your lungs fill with air, and you are not filling them completely or properly. Why we start to breathe "the wrong way" I don't really know, and they didn't bother explaining this to me, but whatever lol.
So keeping this in mind, take a proper deep breathe in for 8 counts and then out for as long for you can, concentrating on breathing from your stomach and essentially the bottom for your lungs, and filling them top to bottom. Keep your shoulders relaxed, and make sure you don't tense them. The breathing should be relaxed and if you put your hand on your stomach you should be able to feel it move up and down as you breathe in and out.
Once I got into the habit of breathing like this (its second nature now, even while im sitting here in front of the computer or running), we moved on to learning the air aspect of producing sound. First they had me take in a breathe and then blow it out (while forming an embouchure with my lips). Then I was told to tighten my glutes and abs, and blow out. During both experiments, they held a piece of paper in front of me. The first time the paper moved, then when I tighten my abs and had me try again, and the paper acted like it had been shot. Essentially, by tightening your muscles below your lungs, you expel your air quickly and can do so for a long time with practice due to the increased air in your lungs because of proper breathing technique.
Now putting the breathing aspect together and the lips lesson together, they added one last thing in. And they both wrapped up with basically the same thing. On top of using proper air, you need to learn to properly focus the air, and if both are combined, high notes will no longer become out of sight, and you won't be shoving your horn into your face as hard as your arms allow you too. They had me do yet another quick experiment. This is another pretty easy one. They had me breathe in and then blow out (with proper technique, and tightening of my abs/glutes) while pulling my corners back and my lips tight, and then putting my hand in front of my mouth. The air was flimsy and it came out almost in a line. Then they told me to make almost a pucker, by bringing my corners in, and try again. The air almost shot out of my mouth, and was a round and focused when it hit my hand, only hitting a the part directly in front of it.
After that, it clicked for me, both times (when i got my braces on and when I got them removed), that 3 basic things lead to a greater range:
-proper breathing, filling the lungs bottom to top
-using your abs and glutes to exhale the air quickly and with pressure behind it
-by focusing the air with your lips, instead of pulling your corners back, you can control the speed and direction of the air and in the grand scheme of it all, play higher notes.
I know I rambled on for quite sometime, but if you are in high school like it seems, it might help to know the actual science behind playing and range. Instead of seeing those higher notes as impossible and automatically nailing your horn into your face, you can take them on from a different view point. Its going to take time to build up muscles, and breathing technique is something that has to constantly be worked on and improved upon, but it worked wonders for me, and for these guys (one of which is a very well known lead trumpet player in New York City), it works well too.
I wish you luck with your braces, they shouldn't hinder you for long if you are smart about it. And I hope this method works quite well for you if you are still awake after reading all of this crap lol.