I guess you will get to this in the second part but since that is not up yet I have a small question.
At the end when you say that the current from the LM3080 adjust pin through the 2k resistors isn't exactly zero (LT datasheet says 10uA typical), this will do two thing - make the minimum output voltage higher (10uA*2kOhm = 20mV), and also offset it through the entire range.
So, my noob question is, could you fix it by connecting the inverting terminal of the Vset buffer opamp to the adjust pin directly? This will fix the offset on higher voltages. Also, if there was some low power negative supply for the opamp it could also go down to 0V by driving it's output negative.
Is this correct or am I wrong?