Boy, did you pick a winner, my friend!  IMHO, M4's basic texture shader is an absolute mess. The initial texture map is too red and to compensate, a blue tint was introduced to offset that problem.  Also, there are no gamma correction nodes within that set; you either create it or use BB's VSSProp.  That's why it looks correct without Gc in your render.  No wonder you are having major problems.

First, Gc on the dome does not impact itself on the rest of the image.  You must have Gc imbedded in your mateial or set in your render engine (PoserPro, PP 2010).  If you decide to use Gc in your render settings, then any Gc nodes present in any material must be reset to 1.

Second, I strongely recommend you replace M4's present shaders with BB's VSS.  It will dramatically improve the overall skin texture.  Again, if you are using PP 2010 Gc in the render settings, you must reset Gc values in the VSS to 1!

Third, the envsphere is providing ambient lighting for IDL to calculate global illumination.  If you understand the concept of IBL ( a cheat, btw), that is what IDL is doing.  Except, it is calculating color reflectance of closely associated surfaces within a defined space (like a room or envsphere).  

Your last image appears correct because there is no Gc applied in either the skin shaders or the render itself.  And there is no image in you envsphere to apply any Gc; gamma corrected white is still white.  Think about it a little further, and if you still have misgivings, let me know and I will fire off some demo renders.  I am not at my home computer at the moment, so will you need to give me some time.

I'll get you through this, promise.