Utility should not be confined to science, merely checked against it. Truthfully, I view Jung's personality through the same lens as you do the Enneagram. Hopefully Dr. Nardi is able to churn out more neurological research on Jung's theory, however; scientific validation of any personality model would, I believe, fight the wave of standardized behavior that is currently corrupting the mental health industry.
That description fits - I am fiercely individualistic - but I am still wary of binding a correlation to causation. It is very easy to use post-hoc rationalization to fit one's self into the parameters of a given personality, a label that, at the end of the day, is relevant only for identification purposes. I'm guilty of this at times with Jung's theory. In the past year or so, I have focused more on motivation, achievement, and emotion to understand myself and assist others than personality. I still think the latter is useful as an organization heuristic, but I will not treat it as more at this point. I hope to one day be able to soundly revise this habit, but, well, all in due time.
Reluctance to share one's thoughts and ideas is normal: criticism is uncomfortable and rejection can be outright painful. Humans crave order and security more than anything else, I think, and threats to their sense of self undermines both. Humor and an awareness of scale - where you are versus where you want to and can be - can make things less dire. I am glad to hear your parenting skills have improved ^.^