A 10% ambiant light from sky will always make the image darker with more contrast, so I wouldn't go so extreme. Your light balance has no sunlight at all, well 3% only, so it has to be dark, and puting more skydome lighting gain won't change a bit, since you killed the light coming from the sun. For interior scenes, I always use fill lights, even with radiosity, and even in other 3D apps like C4D. Also, in real life, I'm not sure the opening in the roof and along the wall would produce enough light to get a full daylight in the room. One parameter you may need to increase too, is the radiosity gain.