Sorry if this thought has been tossed around a lot, but since I left the forum yesterday around 5PM CST there have been over 1000 posts.
I have found during my time working with sex offenders, pedophiles, and sexual sadists, I have found that when these people tend to hook up with adults that appear very child like. I would be very interested in interviewing the girlfriend to see what MH's personal behaviors were like in the time they were together.
Also, if MH is a psychopath (I highly suspect that he is), he would be getting quite a bit of satisfaction out of "stumping" the police in this case. It is not unusual for them to stay near a crime scene, or to check in on his victims after he leaves them in order to see how close LE can get without finding anything. He likely "cooperated" in a way that would have made him feel very important to the case, without actually giving LE any legitimate information. He will also likely not incriminate himself in any way. One thing about most people that engage in this type of behavior is that everything they do is very purposeful; even to the point of being overly controlled and planned.
Control seems to be the main focus in the lives of most people that engage in this type of behavior. He would have been very controlling in his personal relationships after the "honeymooon period" wore off. He likely feels that many aspects of his life are very out of control, and that because of that he has to exert extreme control on other areas of his life (or the lives of others). He would not have had any problems controlling 4 people and getting them to do exactly what he wanted. He would also likely have made a "showing of power" to the victims in the home before he took them anywhere. This is the most likely explanation of the blood in the home IMO. Unless LE is able to convince him that his most powerful move would be to send them to the place where the remaining victims are he will likely continue to string them on in a way that allows him to feel powerful by playing with people's emotions.
Sorry for the length. I just did a lot of reading and had to vent for a minute.