Responses
As for point one, as a child, Ryo was probably too young and traumatized. As he aged into knowing better he was able to "benefit" from the relationship by recieving stuff. This could be why he never alerted anyone. He may also have not want Natsu to grow up fatherless (although he kind of already did).
If nothing else, polititions are slippery fellow whom can kill puppies and still appeal to the people.
I like dark and dramatic stories, and this is one of them. It's good, but if you can't handle the graphic nature of it stay away; Anyways 2 things really bugged me 1) with the pedo-rape video tapes, Ryo could have protected Natsu by getting the dad in jail (or better yet castrated!). and 2) wtf why was the ending like, "I wonder what dad thinks in heaven?" no way is that dipsh*t even remotely near heaven in his afterlife...