I really liked the idea of the dreaming theme and the observations that Sam made. I sort of feel like to assert that memories were an intentional aspect of the film requires more evidence, but it's a fascinating angle. On that topic, some other things that I noticed within that theme/motif:
1. Jeffrey's nightmares (okay, obvious).
2. The various picturesque, Norman Rockwell-reminiscent images, like the flowers and the fireman and the children at the crosswalk, and later on, the dance Sandy and Jeffrey attended. These images, far-removed from the nasty underbelly of Frank, are dream like.
3.Conversely, the more ridiculous awful scenes (out in the field, the first time Jeffrey sees Frank, the well-dressed-man costume [what?!], etc) play so much like nightmares or bad, distorted memories.
4. Dorothy is very... deluded--all the time. This puts her on a different plane from everyone. Actually, I can expand this to Frank too. Their separate plane from the "sane" people feeds back into the idea of not being in one's correct and accurate concioussness, dreams, and memories.