I like your writing - simple and crisp. There are a few flaws.

Your main character is supposedly six. The dialogue is completely unbelievable coming from six-year-olds. No librarian would let a child take out a book called "Humans and Sex" without serious questioning first. In fact, I think all the flaws come down to the same thing - it's just not believable. Even if you were planning on taking this story to 'fantastic/horrific' places, everything comes down to your readers buying the characters.

Child abuse is a tricky subject to write about. So far what you've written comes off as trite, like you just wanted something to motivate/hurt your main character. It seems thrown in for shock value. Maybe you're just building to something I can't see, but because of the problems with character, it's hard to see anything but the technical (writing which is, as I said, good).

I think you're brave to take on a dark subject, and wish you luck.