Why does my ground current look like this (and why is my current so low)?
The current spikes in the Source are the result of very rapid charging and discharging of the Gate-Source capacitance. A realistic circuit would have some resistance in the Gate driver, then the Gate-Source current spikes would be smaller (and the FET would take longer to turn on and off). 

Source current doesn't actually drop to zero when the FET is on, it just looks that way because 60mA is so much smaller than 10A.

Drain current is low because L1's inductance slows down the current rise. Inductor current = voltage x time / inductance. At 200KHz and 50% PWM the FET is on for 2.5us, so 15V x 2.5us / 3mH = 12.5mA. 

If the FET had zero capacitance then current would ramp up to 12.5mA while it was turned on and fall to zero when it turned off. But the IXFB210N30P3 has large output capacitance which supplies current to the inductor when the FET is off, causing it to continue rising. Eventually it 'walks' up to about 60mA, ramping up and down by ~12.5mA as the FET turns on and off. 

Reduce the PWM frequency to about 20kHz and you should see the current variation increase as the inductor is given more time to allow it. The current waveform will then become a sawtooth, and the inductor will resonate with the FET's output capacitance to produce a very high voltage spike when the FET turns off.