With your park brake off and wheels chocked is there a leak you can hear when walking around the unit. From your description it sounds like a brake pot could be leaking. Note you need to have air pressure built up to do this simple check
As you go through the motor home you will discover more of them, they are probably for options that you don’t have. I think they had there harnesses made up to make one size fit all and some connections weren’t used for different models. That is my theory as I have discovered them on my unit as well and everything on the unit is working
You could try 3m vhb ( very high bond) in short pieces can’t it move once applied I use it hold my solar panels on the roof 4 years and still can’t move them. If you have to get it off you need a razor knife to cut between the two surfaces. Scrapers and lacquer thinners to remove residue can be got at the big box store. Try it on a piece of scrap first
On my unit I shut off the system heat in am turn on at bedtime and I can see the remote temp gauge rising so I know the heater has reset. Yes my fan will continue running after the heater has shut down
Just did the same job in a 2001 diplomat, went with a fridgadair 1425 was a easy job and everything came thru the door, as a plus got a 7” broom closet on one side of the fridge. Was able to keep furnace with no modifications
Just did the same job last week, wasn’t to bad had a young strong grandson for the heavy lifting. Replaced with residential Frigidaire was 7” narrower made a nice broom closet in the space left over