Why is the well only 13 feet deep? Did you run into bedrock? Ideal would be to have a deeper well. If the footvalve could be set down 30 feet, the shallow well limit of the pump would prevent it from ever pumping it dry.
Take a look at the Cycle Sensor. It senses the current draw to shut down the pump. I don't know if it would react fast enough to not lose prime, but maybe Cary can chime in here and advise.