That's not much but it's something
1) care about your shadows shape (ball, the core shadow is under sight line so it is an elipse [lazy one in my case])
2) strong light strong bounce shadows! Closer to the bouncing plane stronger the bounced light
3) there won't be an occlusion in the corners of the light plane, it is obliterated by the light
edit. this side walls are definitely far too bright for being parallel to the light direction! Even with the bounced light from the floor