By adding an Edge_Blend node into the light shader, I was able to cancel out most of the viewing-angle dependent changes. 

I plugged the Ratio node into both Inner_Color and Outer_Color of the Edge_Blend. The Inner_Color was set to RGB(47, 47, 47). The Outer_Color was WHITE RGB(255, 255, 255). The Attenuation was 1.

The Edge_Blend is then plugged into the Light Insity, where the Ratio node used to go. As compensation, I had to rais the Intensity. Where before it was .05, now it was .18.

These settings are not exactly right, but directionally correct.