Judging from the looks of your surroundings; you've got access to a nice facility and already had some good pitching instruction. Some of the harder throwers I've seen get their front knee back over the rubber further and show their back pocket more but that makes it a little harder to repeat consistently. I don't think there's anything wrong with weighted balls......4 and 6 oz out of season. Don't get crazy with them. Play some other sports if you have the chance. I think you've got a great start. When that guy on the bucket starts hiding behind the bucket you'll know you've made progress.
Get a good four week foundation of throwing first when you are coming in from an extended layoff. Then I suggest getting right at it in practice. Make sure you take time to stretch and get your core warmed up. (This is something you can't cheat on) then throw the dang thing like you mean it. But work your way up to max speed and maintain your mechanics. You might start out throwing short to the catcher for accuracy and then move back to the rubber. If you throw hard in the pen you can take it out on the field with you.
Protect The Arm?
Tuff Cuff, Throwers Ten or ASMI RTC exercises. This should be a religion to you! At your age you might have someone holding you accountable. When you get to be a senior in HS or go to college it has to be second nature. The longer you go without rehab the better.
I like what I see.....just one more thing. Whoever helps you along the way...make sure they know you appreciate it. 8)