There aren't any laws prohibiting installation of CB radios in vehicles, and you don't need a special license to operate a CB station. CB radio rules are under the jurisdiction of the FCC.
1. When is "operating in full compliance with local laws and regulations" unethical?
The invention of the radio did cause for some new laws to be enacted. Specifically laws regarding what can and cannot be broadcast over the airwaves.
A truck driver's responsibilities include obeying all laws and regulations related to transport of goods (and there are a lot of them), obeying the rules at each freight terminal visited, protecting loads from theft or damage, driving the truck safely, maintaining his equipment to include maintaining a fuel level sufficient to make the trip, and operating profitably.
It depend on local ordinances and laws
Depends on the state laws.
Laws on this vary by jurisdiction.
Most definitely
Ussually in most cases the local laws and customs prevail
Depends on the laws in your jurisdiction.
Local laws may vary. Typicaly noise laws are to not make a lot of noise after 10 pm. You can check your city code.
The question can't be answered as asked. It depends on state laws, and laws are different in different states.
Radio waves are controlled by the people who operate transmitting devices and by the laws of nature, not by the government. The government controls access to the privilege of operating transmitting devices. If that access were not controlled, the entire radio spectrum would sound like the 27 MHz 'citizen's band', and nobody would get any productive use out of it. Including would-be police, fire, ambulance, and cellphone users.