Am I correct in believing that 9v is way too high to for an analog in?
Yes. The maximum input is slightly above VCC. Most Arduino boards VCC is 5V. In the case of the Analog Inputs, anything above AREF (which is typically the same as VCC) will read as 1023.
Does the onboard Arduino voltage regulator also work for analog inputs or is that just for the DC connector
Voltage regulators are for powering devices and have nothing to do with inputs. It wouldn't make sense to put a voltage you want to monitor into a voltage regulator. Because you would always get the same voltage "out".
You need a voltage divider