The 800-1100 ADUs calculation using the Cloudy Nights tables already take heavy background light pollution into account. And that is ABOVE the dark value, so 700 + 1100 = 1800 I just added another 100 -200ADUs, because the pollution is REALLY heavy at my location.
The exact value one has to determine empirically, I think. But the tables get you pretty close to the optimal setting. Going to less than 1500 ADUs mean for my location, the signal gets decidedly wimpy, going higher than 2600 I am clipping too much at the top end. Much of this then comes down to judgment, I think.
Of course, in Bortle 2/3 skies all these considerations are moot. There, you can use the full dynamic range the camera offers. You are so lucky!