Could you have a the barn boards planed thinner. If you only plane one side it won't affect the look.
I would switch to a different type of box that allows the proper mounting. There is no reason to use box extenders when you know the proper depth...
The only to be sure where the property line is located is a survey.
Dehumidifier and insulate the pipe to keep the moist air away from it.
Plastic plug in the pressure tank pipe to keep debris out when shipping?
Your plumber is correct.
Even if it kicks on every flush stuff is still in there. It does not get pumped dry. There is always a few inches of...
You can do that but you need to determine which breaker they are on. They won't be connected directly to the main.
No. You are not allowed to alter or add to an ungrounded circuit.
Separate names with a comma.