The title

Excellent question. I was wondering about that myself. Apparently, in the book that the movie is very loosely based on, there's some philosophical and religious musing by the protagonist of both the book and the movie (Baldwin's character) about how the victimized children are in a way the prisoners of the idea or rules of Heaven. I haven't read the book, but I think the idea in the book is that kids are raised to expect that the world around them is heavenly and that Heaven will keep them safe on Earth, but once the circumstances change or the kids grow up they become victims of this "teaching" because they don't know how to function in the real brutal world. Or, it's the idea that if Heaven is real and they need to abide by its laws, this stops them from doing what needs to be done in order for them to keep themselves safe in the real world. Something to that effect, I think. None of this is carried over from the book into the movie of course, so at best the obvious meaning in the movie could be that these tragic and vicious characters are stuck in heaven on Earth (Florida) that's actually more like hell.