Welcome, Jim, to the OEM forum.
I’ll answer what I can, I need to leave the other points to those who know those areas better.
That’s OK - the 9 V output is on full load, the load the Shield provides is “minimal” - almost nothing. Depending on exactly which adapter you have (UK, EU, US) the output voltage is 11.6 V ±3%, 11.6 V ±5% or 12.0 V ±5% respectively at the nominal mains voltage.
The voltage calibration constant is the mains voltage that would give 1.0 V at the ADC input - this is after the resistive voltage divider on the Shield. The same goes for your c.t. - in this case it’s the current that gives 1.0 V at the ADC input, which in this case is the jack socket.
I’m by no means a RPi expert, but my crib notes say
“Serial USB connection to Raspberry Pi: The address you need to use in emonhub will be /dev/ttyACM0 (assuming this is the first/only arduino connected) instead of the usual /dev/ttyAMA0”
This might help: Multiple emonTX Serial connections - #2 by borpin