First, it's Amaterasu. Second, she's the August Goddess of the Sun and Ruler of Heaven (Shinto Heaven), not a creation deity (though the Emperors are said to have descended from hers and Susano-o's children). Amaterasu is the child of the creation deities Izanami and Izanagi, who are said to have created Japan. They in turn were created by Kunitokotachi and Amenominakanushi, two primordial Gods, and given the task of making the land.
Third, I doubt it can heal all wounds, sadly things don't seem to do that often. The mirror, or Yata No Kagami as it is called in Japanese, was powerful because it reminded Amaterasu of who she was when she had lost her way. After a large disagreement with her brother Susano-o, she hid within a cave for sometime. Her absence also took the sun with her, and light was removed from Japan. Several Gods and Goddesses developed a ruse involving the Goddess Uzume dancing in front of the cave to the uproarious laughter of the other Deities present. Amaterasu was intrigued, and left the cave to see what eople could possibly be rejoicing about. When she did Tajikarawo, the God of Force (and Uzume's husband), rushed and blocked the caves entrance. Then the mirror was brought forth, and when Amaterasu looked into it she was reminded of her duty and pride, both of which she had neglected, and she took again her position as ruler. This is a reason why mirrors are hung at the entrances of Shinto shrines, to remind people to remember themselves.
Fourth, If indeed the mirror the royal family possesses is the same one, and I see no reason to doubt it, it would be of great use to practitioners of Japanese magic, but you don't need it. I live in and have never left America but I still worship Amaterasu and a few other Japanese Deities. I use a mirror in my worship of Amaterasu and create my own Shikkigami, dolls used for the equivalent of Familiars. Just research and come with an open mind and you can learn almost anything.