Maybe I'm doing something wrong, but I can't get the plots to show the change in Vout when R2 in the schematic is stepped. I can see the value of R2 being stepped in the plots, but Vout stays constant. Vout should change from 100 uV down to 1 uV as R2 is increased from min to max resistance. The CD Op point works OK (2nd and 3rd pics below). The 4th and 5th pics below show the .step issue. Does the .step function in the Mac version of LTSpice work? This is a pretty simple circuit.
1108.Pyrometer Preamp LTC1050.asc
Added actual schematic file Pyrometer Preamp LTC1050.asc
[edited by: pgoodwin at 3:46 PM (GMT 0) on 25 Jul 2020]