What type of fitting is the air inlet?
It's a standard shraeder fitting, just like that on a standard auto tire valve.
Is there an adaptor available to connect the tire gauge to my air compressor via an NPT connection?
No, the EZ-Air is not designed to be connected to a compressor in this manner. There is no trigger mechanism on the tire gauge to initiate/stop airflow.
It is designed to attach to the valve stem on the tire using the clip on chuck. The air compressor hose is applied to the other end of the tire gauge (shraeder fitting) to air the tire.
Can I get a right angle clip on chuck on the EZ-Air?
No, the only chuck available is the straight clip on chuck shown.