A lot of water inside the headlight after a wash indicates to me that the seal between the two sections of the headlight assembly is leaking. This needs to be sealed with silicone sealant or similar. Excessive amounts of water after a car wash cannot be put down to humidity in the air when you think about it. I have the original vents on the rear of my lamps and I have no moisture problems.
Fix the leak for starters and go from there.