Is this a map of Japanese territorial waters? Why is there an empty space in the middle? How come the Diaoyu Islands are within its scope?

The first question: Not all of them are maps of Japanese territory (sea), they are entirely Japan’s wishful thinking.

As you have questioned, the Diaoyu Islands, Ryukyu Islands, the Four Northern Islands, and Dokdo are not Japanese. It was snatched by Japan during World War II, and it was stipulated after World War II that it does not belong to Japan. Due to the intervention of the United States, the power of the Ryukyu Islands was unilaterally handed over to Japan for management, but the sovereignty is not Japan's. (This is another topic, so I won’t introduce it in depth. If you want to know more about it, you can look up the history of the Ryukyu Kingdom and the post-war Ryukyu Kingdom (Okinawa)).

Second question: Why is there a part in the middle? First of all, we must understand the division of territorial sea. It is the number of nautical miles (I forgot) from the center of the land or island (note that it is an island) to the surrounding areas as the territorial sea. Plus the exclusive economic zone and so on. In fact, Okinotori Reef (called Okinotori Island by the Japanese side) is actually just a coral reef. It is not an island and should not have such a large scope. In order to expand its own interests, Japan insists on calling it an island, but China does not recognize it.

The third question: It’s a similar situation. I don’t know the specific situation very well, so I won’t answer you.