Orange mapping is great for finding out if some of the rooms are too big. It doesn’t hurt so much to scrap them if you haven’t spent too much time texturing.
As for the lighting, I don’t support the inverted light_spot. It might light up models incorrectly. I would suggest you use the light_spot to point down, and put a normal light entity up there. Just make it dim. Set brightness to 5-10.
I think you could even set it to quadratic 0, linear 0 and constant 1, since it’s for ambient. If it’s the only light in a huge room, you might want to set maximum distance the light is allowed to cast so it wouldn’t look all goofy. I can’t say for sure how well this will work, since I just thought of it. So you might want to tinker with those values.
Or just do as I’ve done so far, just slab the light there, make it dim and worry about the other properties later.
Of course the 50/0 percent falloff distance is a simpler way to control the light, so you should try different values there and see how it looks.