Are you saying that you experience many realities, or that somehow all people in the world could be one persona?
A little bit of both, I guess. I'm still unsure as to the specific metaphysics of this little gedanken, since I don't actually believe in the concrete reality of anything that could be called a soul and therefore am not sure how to handle it.

You choose to be unable to choose... the very act of deciding whether or not you believe it is already decided.
But someone's belief or lack of belief in free will doesn't have any impact on whether they actually have it or not. If they do have free will and choose not to believe that they do, it's still their choice to believe that.