Yes, that's exactly how I use it. I've also had use cases where I needed something now and didn't mind a plastic part for actual use because I knew the load would be light.
OK, but you use very little amounts of the refrigerant. 1 pound of refrigerant that’s in a closed loop is the same as 1 ton of CO2, which is about the equivalent of burning one tree over 20 year period and that’s assuming it leaks out which it’s not supposed to.
One, a beer gallon, the other a wine gallon. The US still also has 'dry gallons' for things like pints of blueberries.