Rich, thanks for the openness of your post. You are quite correct to delay a bit in teaching others the impediment concept of shame until you have more of a chance to grapple with it and believe it. It is not immediately obvious to anyone that impediment to positive affect triggers one of the shame family of emotions. In fact, understanding Tomkins's chapter on shame in "Affect, Imagery, Consciousness" Volume I required more meetings of Don's and my original study group than any other chapter.
One way to think about it is this: we have two basic classes of affect, positive and negative. Tomkins perceived that the affect system evolved to provide us with a means of amplifying all the information entering the central nervous system through our senses. When a stimulus is amplified by an affect, we are much more likely to become consciously aware of that stimulus and attend to it. In fact, we do not become aware of anything unless it triggers an affect. Add to this that positive affect is inherently rewarding and negative affect inherently punishing.
Given these facts, it is only logical that evolution would have granted us a means of knowing when a positive affect that we want to maintain is blocked in some way. If the positive affect has come to its normal conclusion, i.e., we are not longer interested in something, then we need no signal. But if we are still interested in something or still enjoying it and something impedes our interest or enjoyment, a signal is of great use to us so that we can remove the impediment and go back to our interesting or enjoyable pursuit. Otherwise, our ability to maintain interest or enjoyment would become a random phenomenon as we would have very little control over it.
The signal that interest or enjoyment is being impeded must be a negative one (punishing) because if it were rewarding (another positive affect), it would be as confusing as having no signal at all. As a result, when interest or enjoyment in another (intimacy) is impeded in some way, shame is triggered to signal us that an impediment has taken place. In interpersonal situations, shame is experienced as a negative feeling that most people would call something like rejection, isolation, or feeling distant from the other.
I hope this adds another small piece to the development of your understanding of shame.