Can the reference voltage be output to a pin somehow? Then I could buffer it and carry it to the points needed to get the full ADC measurement range and not have to attempt to match it externally ... which will always be off.

The Vref for ADC conversion is noted briefly in the docs as 1.8v but there seems to be little mention of how to get the Vref signal off of the chip or how to get an external Vref into the chip in order to set the driving voltage to external sources in order to get accurate analog measurements. I've ...