Not sure what you are asking but there is nothing that can be done from a legal perspective.

The issue here is you neighbor, not the post office. Sue him in small claims court.

No you can not. Recycle or throw them away.

Yes he can. Report him to the police....

The decision of whether he has to testify will likely be made by the judge, in response to motions filed by your attorney and the state's attorney.

This is missing a lot of context but if he is living in your trailer, the park can likely ban him. He needs to speak to a local landlord/tenant...

The short answer is he needs to retain a traffic ticket attorney in the county where he is supposed to appear. They can likely appear for him.

Probably not. Lawsuits are expensive and time consuming, and you have to prove damages. Better to either call the cops or seek a restraining order.

In libel cases truth is an absolute defense. So as long as what she said was true, she cannot be sued.

It is possible because you agreed to it when you bought the car.