I think your lights are too bright when used in combination with gamma correction, causing the skin to look washed out. Gamma correction doesn't change the hue of the base texture, so VSS probably isn't causing the yellowish look. If anything, the sub-surface scattering will make the edges of the figure look more red. If you're using VSS PR2 or PR3, you should definitely reduce the intensity of the Indoor lights, which were released for VSS PR1. I've heard the intensity should be halved to compensate for the gamma correction.

I can't help you with the artifacts though. The AO sample number might need to be increased or the bias might need to be decreased. You also might want to try increasing the Irradiance Caching and decreasing the Min Shading Rate, though neither of those fixed the problem for me when I had it. I'd also like to know what causes those spots because I get them from time to time.