>forearms
Do wrist curls and towel wringing at the end of your routine.
Lift using free weights and whilst doing lifts involving them grip as tightly as possible whilst focusing on stability and form.
>sprinting
Just practice I guess, but do it on a surface that can absorb impact so as to avoid injury. Your ankles will take a lot of abuse so ease yourself into it whilst taking foods or supplements involved in their repair like vitamin c. Ankle injuries can take months to heal.
>Throwing strength
Work on muscles involved. These are the biceps, triceps, shoulders, back and core