I'm not a psychologist, and I don't really have solid answers to the above questions, but I plan to post my musings on such questions and related ideas on this blog.
While I don't really have any answers for these questions, I do think about them a lot. My concept of reality is events flowing along the time stream. Reality is defined by events that occur in sequence along the time stream, and therefore really happen in our universe.
But how can one discern between the "real" universe and fantasy universes (such as dreams). This is something that I still haven't fully figured out. If a fantasy universe contained enough real elements and could feel real, how could a person know for sure that it isn't really a reality. For that matter, why can't there be multiple realities happening almost simultaneously?
For now, I'll continue to dwell on this topic and hopefully in the future I'll have more to share. In the meantime, leave your comments below, or you can contact me on Google Buzz or Twitter.