Yes - 10k - the I2C section is working great.
Further study is showing the prob may be that the FREQUENCY of my stepping pulses may be too high. This project will be used for indexing parts in a milling machine - to cut gears. Each press of the run button makes it step some increment. I've set the code to run continuously when the Run button is pressed (I can stop it with Arduino reset). When I do this I can hear the motor 'singing' and not stepping - the signal to the STEP pin is a 1 KHZ, 50% duty-cycle square wave. Will try reducing that...
=A.