Toaster Oven Reflow Thermocouple Grounding
After removing the duplicate ground from the USB port and powering via a DC 5V adapter (common with the micro) it works. However, I noticed the readings were very slow to respond. I didn't feel like it was worth the effort to try and completely isolate the thermocouple from the grounded chassis, so I purchased a different thermocouple that has a fiberglass jacket and upgraded to the MAX31855. 

Readings are much more stable now and faster to react. Thanks again!