I wouldn't be too gungho about deleting material nodes unless you understand exactly what and why you are altering the connections.  There may be effects you desire which could, potentially, be lost by the changes. 

Do reduce your texture size in a 2D program; there is no need for high resolution unless you are rendering closeups.  Also, reduce your Diffuse_Values on the PoserSurfaces to 0.8 (80%) or more, if necessary.  No surface reflects 100% diffuse lighting, you will just increase your render time.

The overall grayness may be attributed to Gc, however, I don't think so.  Usually, this occurs with too much Gc.  Without seeing your render settings, it will be hard to determine what is actually the problem.