Well, I can add that Microsoft support is pretty darn good (I'll give them that much). They spent three hours on the phone while controlling my PC. While almost everything they tried I had done previously, I was surprised at the patience and diligence of support to sit there through each of my lengthy boots and the long process of watching 8.1 trying to install.
My issue has been escalated to tier 2 support, and they are going to continue with me tomorrow. I'm trying to take notes to see if there is any one thing that stands out in what they do (assuming this gets fixed).