Firstly a digital pot has to have a supply range equal or exceeding the analog voltages involved or you'll
risk frying it.
It seems to have a +/-10V differential analog control mode (page 16), which could be interfaced to
using a DAC and opamp to boost the ouput of the DAC to the +/-10V range (it seems that S1 and S3 may
be +/-10V supplies from what you describe).
It seems the controller doesn't have an opto isolated PWM control input, alas.