wow this is nuts im the exact same size the same hand and same age as u lo.... im probably gonna work on what most people put here but for what i can give you id go with shoulders chest and core
core for balance, shouders for duribility and endurance, and chest for velocity. You need all 3 of these to throw harder balance is needed to keep your mechanics in place, duribility for your ability to throw full out longer, and chest because they are major muscles in the slingshot effect when you throw. Look at any open side or front view of any pitcher and you will see a serious flex on the chest, particulary the pecs...
you can work all 3 areas with just push-ups and situps or planks just make sure u do broad arm (arms far apart) push ups for more chest and inverted or regular ( inverted is arms close together) pushups for shoulders.. situps can be done many ways i particularly like doing a them with your legs up planks are good to though because although there isnt much of a range of motion, they do work your back in some ways which will b needed to support your body.
im no expert but these are the things i do without weights and they will work just fine for at home or when your away and dont have access to a gym