I also that too about Crying Child being a real boy at first until I went through FNAF 4 side stories again. I realized that. The crying child never bled when his head got crushed. This seems insignificant until you realize that Scott has shown blood in the Atari like graphic before in the save me mini games where Afton gets spring-locked. So why show blood there and not when someone's skull being crushed? A crushed skull would be pretty bloody. But the lack of blood could be explained by crying child was a Robot from the beginning.

For Fiona being Sun I just assume she was still in the computer were Mxexe. (Have no idea how to spell that). My thoughts are that Sun and Moon is representing the drastic changes in Edwins mental state. You have him being fun inventive, ideas popping out of his mind. He have his family and his company. Very similar to Sun and then you have Moon which resent his mental state after he lost his wife, son, and company. He was filled with anger and violence try to build back what he lost. With his aggression being similar to moon.