It basically boils down to this "The more I think about it, the more I stutter." When we are able to stay in the moment, with no fear of stuttering, we speak fine. It is when we project our thoughts in the future that we lock up. Ironically, it seems one of the ways to beat a stutter is to give up the struggle - to be Ok with your stutter. If you can give up the anxiety and the fear, the stutter will go away on its own. All of your observations are very common amongst stutterers.