Help on becoming a better baseball player?

Okay so this last spring I played baseball for our high school team who sucked we went 6-22 well I played as a JV catcher and back up catcher for varsity well I want to play Varsity next year as a starting pitcher and third baseman which will be hard since the coaches son plays third and also led the team in errors and I still want to catch a little bit and im an alright fielder an alright catcher except for my blocking if that were better I'd be starter but I'd always get nervous then yelled at for stupid mistakes but anyways I havnt pitched in 3 year it'll be four when I play next spring and I was alright going 7-1 I could've won more but elbo tendenightis ruined my arm till almost the end of the year when it healed I was hurt by a shoulder injury which hurt my arm so much that everypitch I threw was like 10 mph so I pitched a total of 100 pitches in one inning yes 100 and my coach didnt take me out and I was 12 well ever since then I can't throw hard or long and my shoulder still hurts but the other day I played catch for a while and my arm hurt but not as much until after I played for a while and I tried throwing a knuckle ball need help on it please help and my curve ball was great but I want to improve my fast ball speed and endurance also I need hitting tips so yea don't be ***** just help also I want to play basketball and I have a good jumpshot but it just won't go in when I shoot so please help on that I haven't played since I was 12