What do i need to work on to be a halfback?

You need to lift, and eat a lot. A 110 pound halfback wont cut it even as a freshman in football. A 5.0 forty isnt very good either. There is a lot more to playing halfback than size and strength tho. Also depends a lot on agility, balance, and vision. The vision and agility are the toughest things to learn. In general those two cannot be learned. Without them, no one can really be a good halfback. It sounds like you have a lot to work on. Good luck.