I've been a long time lurker but have followed this case from the start.
My feeling is that he had seen her around and become fixated, she may have said 'hi' to him one day and he took his obsession to the next level.
I too am unsure whether she would have been kept in the container, just because of the logistics of weather, chances of being spotted etc.
But I believe that she managed to convince him to release her. I wish I could remember exactly what it was (i'll go and search through the threads), but one of the press releases, whether it was with the sketch or when she first arrived home, it said that AH herself was one of the key aspects of her release, and the media/coverage of her disappearance that helped.
I think that over time he felt he could tell her things etc and talked about his upcoming court cases appearances etc, and I think that Abby managed to convince him that people assumed she was a runaway, he could drop her off where he picked her up, she wouldn't tell anyone where she had been and they could wait and see what would happen at his court appearance and then she could return if he didn't get jail time, if he did then she wouldn't be left alone where she was kept while he was inside etc. (all of this obviously a ruse to help convince him to release her)
This could explain why he stayed at his property, could explain the 'not quite right' sketch (whether LE tweaked it a little so he wouldn't get spooked while they arranged warrants etc) and would explain his looks to her in the courtroom.
All just thoughts going around my head at the moment!