I'm 5'1" - would my foot reach the ground when stopped at a light?

The Minimum Seat Height is 33.5". You probably wouldn't be able to touch the ground very well unless to lean to one side and/or use your tippy-toes or unless you have an inseam of at least that length.

I live at the bottom of a steep hill. What's the best way to get up the hill without burning out the motor or my knee caps?

A combination of using the throttle, pedal assist, and pedaling can be used for large and/or steep hills. The pedal assist level can be turned up as needed if pedaling becomes too challenging.

While the BAM e-bikes can handle up to a 15 degree incline, it is not recommended to exceed 500 watts of power when traveling up a large hill, in order to prevent straining the motor.  (There is a wattage indicator on the dash assembly/display that will show real time the wattage being used.)