Measuring Voltage drop across MOSFET 2N7000
Just realized I measured the current.  Just answering the question for anyone suffering from too little sleep and missing the obvious...

I measured the current and can calculate voltage drop across the 330 Ohm resistor with current.

e.g. 330Ohm x 2mA = 0.66V

Then I can subtract that drop with Vdd and that's the drop across the MOSFET.