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Yes, Freon can be dangerous if released into a very confined area. It will displace the air. It will actually flow to the lowest point in that area because it is heavier than air. When I check for leaks, I sweep the floor boards below the evaporator coil, under seals and fittings. Let alone all around them.
Yes, it can freeze the skin if some liquid gets on you or into your eyes.
Yes, when Freon is burnt the burned the gas turns into mustard gas. If you breathe a good dose you may become nauseated. Freon is not explosive like a propane gas that was mentioned.
As far as the expansion valve, you can not remove it without opening the system.
Some expansion valves are adjustable from the outside. It is 50/50 chance that your car has one because they are more expensive. If it does, it will have a cap that is removable and the adjustment is under it. It can be done without opening the system. This is a sensitive adjustment. Not for amateurs.
To set them properly a temperature measurement is taken at the last (tail) pipe of the evaporator and then another further down the pipe or suction pressure/ temperature reading. This setting is called a superheat adjustment. You are checking for the most liquid droplets at the end of the evaporator and then seeing that is flashes off properly, before getting back to the compressor, which will be the temperature difference. Usually 7 to 12 degrees of rise depending on system design. Only real savvy technicians get into tweaking. This is an advantage of an expansion valve system.
70 degrees is not too bad. A specification of 55 to 60 at the center vent is more desirable. Whether this system can deliver it, is a subject that goes back a ways on these cars. The area of the country and a persons comfort level.
What you may want to do is check the location/fitment of the sensing tube from the power head on the expansion valve. The power head has a gas inside it that reacts to the coldness of the coil and throttles the refrigerant. It should be located as close to the tail end of the evaporator. On the upper side of the tube at about the two "O" clock position. Compressor oil migrates in the gas on the bottom due to gravity. It must be fitting to the tube tightly to sense the tube. Insulated from air flow makes it more influenced by the liquid in the tube but not always possible.
Relocating this may help flood the evaporator better and can be done without opening the system. I don't know if there is a provision for this adjustment but may be worth looking into with your A/C man or possibly experimenting with it if you are so inclined.
Phil
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