What factors could the skater change to apply the same amount of torque but increase the rate of his spin

The moment of inertia should be decreased.

Explanation:

The torque is given by

Torque = Moment of inertia x angular velocity

To keep the torque constant, the spin rate be increased when the moment of inertia decreases.  

The moment of inertia of the body are the efforts to put the object in rotation.  

the answer is neither ball has a charge.

because if they were both positively charged, they will repel each other.

if they were positively and negatively charged, they will seek.