Frank:

I looked at those pictures.

Check the top of the copper tube that makes a loop in picture 2dmf2p5. It looks kinda wet or oily at the top of that tube, but it might just be brazing flux. Maybe clean that tube with some mineral spirits to remove any residual flux, and see if it gets oily looking again.

The lack of any serious accumulation of frost on that evaporator suggests to me that the fridge finished a defrost cycle just a little while before you took those pictures of the evaporator. Maybe leave that replaceable cover off and take a look at the evaporator whenever you open the freezer compartment. You SHOULD be seeing a lot more frost on that evaporator than you see in the pictures.

There's an awful lot of dust on the condensor coils and the condenser fan blades. I'm wondering if what's causing you to cough is that you may be allergic to some of the stuff in that dust. If I were you, I would try cleaning the dust off the condenser coil and the condenser fan blades. (Obviously unplug the fridge when you're doing that work.) The worst that could happen is that your fridge would run more efficiently without that dust.