It’s good to hear a young player like yourself talk about how he’s working hard to develop himself. As for lifting I would first ask your Dr if your physically mature enough to start working out with weights. If you aren’t you could really mess up your growth plates, which can cause you a lot of pain and rehab. I would recommend working out using Bands and body weight exercises. This will not only strengthen your muscles, it won’t mess with your growth plates in the process. Also after any working out make sure you are stretching so that you’re keeping the flexibility you need as a pitcher. As for your velocity, your velocity will go up as you get older, mature physically and gain strength. Don’t listen or try to compare yourself to anyone else. Be the best pitcher you can be. 53 and able to throw strikes at will is a lot better than 57 and not able to throw strikes. You’re only 12 years old, enjoy being a 12 year old, throw a FB you can locate at will and learn how to throw a CHange Up the most underrated pitch of all time. You control and command those two pitches you don’t need to worry about velocity. To top everything off, your velocity is God given my boy, either you’re going to throw hard or you aren’t. Again be the best YOU you can be. Good luck!!