I have a technical question about her broadcasts. How was it that American servicemen were able to listen to her? What radio frequency were the Japanese using and was it really strong enough to be heard throughout the entire Pacific theater?

I'm sure it's debatable as to how much coercion was involved with influencing her to make the broadcasts, but she wasn't the only Japanese-American stuck in that type of situation during the war. For example, in Mitsuru Yoshida's Requiem for Battleship Yamato he describes how one of his crewmembers on the ship was an American citizen of Japanese descent who had been trapped in Japan on a visit when the war started. He was later forcibly drafted into the IJN. In spite of the hostilities, he was able to continue to communicate with his mother in the US by letter throughout the war (I don't know if she was interned or not). One of his brothers was serving in a US Army Nisei unit in Europe. Because of his American heritage, he was mercilessly bullied by his fellow shipmates. He died when Yamato went down.