Thanks. I simulated it in LTSpice and looks like the gain is always constant, the resistors just move the zero and change the whole gain:

The datasheet of the DAC says that the REF output is stable up to 100 uA, so I changed the resistors to higher values to be in the safe region. I built the full circuit diagram on a breadboard, with a OPA4188 with very low offset voltage and "zero drift":

Looks like it works. I guess C2 is to compensate for higher frequencies and I have to try it out for best compensation, but what is the purpose of C7 and R4? Somewhere I've read you shouldn't connect a capacitor to an op-amp output.