I'll play devil's advocate here for a minute- not to contradict you of course, just to debate (because I am 50 50 right now about this guy's character)
I think he could be quite good at leading a double life as earlier reports when he was first arrested, claimed hard working, respectable, devoted family man who didn't go drinking and preferred to stay home. Naturally this was his landlord and I believe neighbours who said that if I recall. I'm very curious to know if he was known locally as a creep by a lot of people???
He wasn't charged with abduction- so I m guessing not overwhelming evidence from the house or car of murder OR a struggle. Or of course, police are building a case.
My thoughts keep going back to the river. Wonder if it is a big river and fast flowing? I still haven't seen it being dragged anywhere?
Not thinking hostage situation is possible either.
I think he might well be an escalating psychopath who was getting more brazen in his activities and getting a thrill off it. Plus he didn't crack under interview- he might be enjoying the drama he is causing? With a narcissistic personality- lies, superiority, lack of empathy etc are all traits.
The sex trafficking- well not very likely- she would be missed within a few hours and transporting her would be hard. She is not anything like a typical victim for trafficking- too high risk.
Just my own opinions