1) Yes, and many times.
2) Yes, but rarely and only in place I know is operated by a Japanese Itamae.
3) Definitely, One major problem is that the names of many seafood and fish are common names and not scientific names. For example, "sea bass" in Japan is suzuki (鱸) (Lateolabrax japonicus), but in other countries it could refer to any one of over 10 species of fish. There is also the problem that some species of fish in Japan is not readily available in other countries such as the US or UK. In Japan, because of the very efficient and streamlined infrastructure that facilitates the selling and transport of fresh raw seafood, you can get fresh seafood that has just been purchase at Tsukiji the same day. In other countries, this is not so and the quality and safety of the raw seafood is unreliable. I've never been sick eating sushi in Japan. But I know some people who ate sushi in other countries and gotten food poisoning.
4) And how is Japan suppose to tell other countries? This is the Information Age (or Internet Age). Any information and subject anyone is interested in or want to learn about is available with a simple search on their web browser. If people in other countries want to know about real sushi, they can already learn about it. If they are not interested, they are not going to be listening.