the spec hotspot on the backwall is ugly, the lightings much improved though…(ignoring the very first image now) i think the saturation is way to high in your second image, but the midpoint for the first is way off. saturation and the levels midpoint are not directly related so you can fix both independently.
Either you should have a nice evenly lit background and no darkening in the corners, or you should have all 4 corners with the same level of darkening. There is a lens effect that will darken the corners and a lighting effect that will darken the background, at the moment you’ve got both, but not consistantly.
that slight rumpled texture you have on the background surface looks like a cheap and nasty studio roll of paper. its necessary to texture everything, but if a studio had something that creased as their backdrop it would annoy anyone shooting onto it.
the shadows are still a little dark. i would put in a low intensity hemi or area light in conjunction with your single spot