Quick thought on WHY SS may have come back to the home after leaving with MS('s body). I think he was not completely sure on what to do, but he had to get her out of there. He dumped her stuff in the dumpster and took off, trying to decide what to do. Maybe he wanted to stash her near the school, or maybe he just drove near it to be seen in the area as if he truly did drop her off. Maybe he then realizes that if she was supposedly abducted near the school, her stuff wouldn't be in their own dumpster. So, he goes back to try and retrieve her items, only now there is more light and maybe more people coming and going and he realizes it won't be simple to grab it back out of a (possibly not very full) deep dumpster without drawing more attention to himself. Maybe he noticed the camera, even. So, he changes his mind again and gets outta there to drive around some more to think about what his next step is.
That's the only thing that really makes sense in my head. He kept panicking and changing plans, which is great for the investigation (hopefully!).