Ok, so you are looking for a more constant flood of light that eliminates the areas of harsh influence by the point lights. There are a couple of ways that come to mind. One is to use only a directional light and turn off cast shadows. What you will be doing is influencing the entire scene. Turning shadows off with eliminate the shadow cast when the directional light hits the outside of the walls you created.
You could also add emission to your materials effectively faking light. My last thought is to add a sky sphere as I suggested in the previous post. As you have walls you will never see it. Then add a sky light to the scene. Without the sky sphere the sky light doesn’t have much influence. However with the sky sphere in your project the sky light can provide a source of ambient light that should effectively add an even illumination.