It sounds like you need to reduce the intensity of the radial light, not the size of it. If you need it bright, another thing you might try is to make a small primitive or a 2D square to block the light from shinning onto the other surfaces. I'd go with the reduced intensity. Also, try playing with the falloff and the ambiance.

Because I like to blow $%&# up.

Don't fear the night.  Fear what hunts at night.