Other mistake: Why hasn't there been a mention of Freddy having a child in previous films? Couldn't be because they covered it up, as soon as Freddy was discovered to be the Springwood slasher the media would have been all over him and his family.
Suggested correction: Throughout the entire series, it's shown that there's sort a miniature conspiracy going on where the people of Springwood have been trying to make everyone forget about Kruger, including actively suppressing evidence. It's possible that when he was initially caught, the media was aware of his daughter, but not only would it not have been that big a deal (they were focused on him- not his family) in the decades that have passed since his original "death", the information was likely covered up or ignored in favor of trying to make everyone forget about it. (Hence, even Maggie doesn't know Freddy is her father.) Furthermore, the fact he has a daughter has basically no impact whatsoever on the story thus far, so it makes sense it hasn't been brought up before.
It has never been shown in any nightmare film that there is a cover up conspiracy until Freddy vs Jason (which takes place 5 years after this film), and that cover up begins after the events in this film, evidenced by many characters saying it's been quiet for 5 years.
Other mistake: If Freddy's powerless in the real world then how does he briefly make his face look normal in the fight against his daughter?