I would be surprised if this crime is as simple as a local RSO. They would know they would be the first to be investigated. I would think if an RSO was determined to carry out such a crime, he would venture outside of the area where he is registered.
It is difficult to whether or not a known sex offender is more likely to be the perp, IMO. In Mickey's case, the perp was registered and known to LE. He made a lot of mistakes that led to him being caught. In the abduction/murder of Kelsey Smith a few years back, the perp did not have a record as an adult at all.
I am not sure what to think about the man they have been questioning. It is possible he simply does not have a provable alibi, as many people probably would not be able to,prove where they were at a certain time (except perhaps via phone and computer records.) but as it seems he is cooperating, it feels less likely to me that he is their man.
I do think this perp must have used a weapon, probably a gun. I can't see her leaving in that way otherwise, for any reason.