What are the penalties for violating federal rule 5 by not sending a copy of document to Plaintiff?

Answer 1

You are referring to Federal Rule of Civil Procedure 5. There can be many penalties, including monetary sanctions under Rule 11. If you file a false proof of service with the court, you are also committing perjury. Other consequence might depending on the type of document being filed such as denial of your motion.

Answer 2

Given your defendent, its possible you could have your case ruled against you, or be hit with a fine.

Answer 3

Contempt of court. The whole case can be invalidated.
Disclosure.