if this were a serial killer there would have been some sort of crime almost exactly like this one. There are certain aspects of serial murder that cannot change, signature cannot change. MO can change and often does change. There would be a crime soemwher involving small children, AE asphyx., molestation--but no penetration, etc. The perp may not use the kidnapping "ruse" again if he/she was unsuccessful, but very well may use it if he was successful.
Also, to be quite honest with you, serial killers are not like they seem in the movies. You seem to think that they are. Please find an instance where a serial killer actually tried to frame a victims family for the crime--with so much staging!**BTW, any Hard core criminal would know that by staging you are leaving much more at the crime scene than you think you are. Many serial killers nowadays know this, many of them are avid "cop groupies" and read detective magazines, etc.