Actually my safety concern is an evaporator leak, flammable gas released inside tha part of the coach we occupy. It'd take a lot of facts to satisfy me that a fuel used as refrigerant isn't more dangerous than a refrigerant used as a refrigerant.
Clutch working... Well, two things. We had a Dodge with aftermarket A/C. I installed it myself and one of the scariest thing I ever did on a car project was cut a shoebox-sized hole out of the middle of the dashboard of a brand new van. Anyhow, after years and years of use, the clutch wouldn't always pop in. I installed a relay. Thermostat triggered Relay, Relay powered Clutch. Worked consistently thereafter.
You're seeing "static pressure." The warmer the weather, the higher the static (system NOT running) pressure you will see if you connect a gauge set to the service ports. I think R12 static pressure in PSI is pretty close to ambient temperature in Degrees F. Nature of refrigerant is such that it'll display the SAME static pressure whether somewhat over full, correct charge, or nearly empty. Good thing about finding pressure is that although it may have leaked down, it's not wide open to the atmosphere. So yes, you could try to charge it up. If your friend is into HVAC, he should be able to find an "oil charge" that adds a couple ounces of oil without having to discharge and open the oil plug on the York. There are cans that contain such a charge and tools that let you add oil to the tool then use it to force the oil into the system through a service port.
