Why does my DC power supply fluctuate and say 0A? And why won't my motor spin?
You seem to have left the STBY pin on your motor driver floating.
The datasheet for the TB6612 driver IC on that board tells us that STBY has an internal 200k pulldown - making the default state of the device Low-Power/Standby (in other words - asleep).
Pull this pin high if you want your circuit to do anything.