1/4. Joe P. wrote, "Averages are meaningless for determining heat" You mean "confusing" (to you), not "meaningless." Set your non-Panasonic microwave oven to half-power. It alternates between full power and zero power with a 50% duty cycle. That heats your coffee just as fast as a half-power microwave oven.

2/4. Joe P. wrote, "160w/m2 bb T is -40C, much too low" You forgot to add roughly 342 W/m² of downwelling LW IR which originates from GHGs in the atmosphere: https://sealevel.info/NCA4_global_energy_flows_diagram_figure2_1_25pct_annot1.png…

3/4. Joe P. wrote, "It's derived after reducing TSI / 4 unnecessarily" It accounts for the fact that the average  irradiance over a sphere is 1/4th of the peak irradiance at the point where the surface of the sphere is perpendicular to the light source. It is not "unnecessary."

4/4. Joe P. wrote, "It's used to offset the difference to the GHE" I have no idea what that's supposed to mean. Joe P. wrote, "A more realistic number would be around 600w/m2" Did you overlook the word "solar?" Even if no sunlight were blocked in the atmosphere, average solar energy reaching the surface would be only 1361/4 = about 340 W/m², not 600.