Regarding the propane smell at the water heater itself, it's probably the gas valve. I had the same problem with my water heater, it worked fine for a few days then you could smell a faint whiff of propane when you walked by it.
The gas valve is spring loaded and opened by an electrical solenoid. When the heater shuts off it cuts current to the valve and it closes. The problem is that the seals inside the valve go bad and so when the valve closes it doesn't completely seal itself.
I found the gas valve
here on Amazon and it fits "most" Atwood water heaters, check your model number to be sure it's the right one for yours.
It's an easy change, be sure you have thread sealant rated for gas use.