Larry, et al.,
I want to chime-in here on one side of the Diabetic/Pre-Diabetic debate -- there is the issue of age. If you visit Larry's profile you will find that he is over 65.
Since the inception of the Pre-Diabetic diagnosis (which was intended to capture the young people before they became Type-2 Diabetics) the vast majority of people being diagnosed as Pre-D's are over-50.
That being said, there are those (Dr. Bernstein, et al.) who hold that the bodily response to glucose must be exactly the same regardless of your age -- if you are 9 or 99 the criteria is exactly the same -- never over 120 and always-always-always rapidly returning to the low 70's after eating any amount of carbs.
The problem I have is that our bodies wear-out over time. The pancreas slows or diminishes in the ability to produce insulin. An inactive body also cannot use the amount of glucose that our society makes available to all people.
What I have noted in this thread is that when Larry works on his diet and exercise he manages to keep his BG levels in check albeit not in the perfect range of 70 - 120 at all times. I, like some others contributing to this thread, am concerned for Larry that his highs are quite high. However, as long as he can maintain an HbA1c of 5.8 without medications that is great!
I have no idea about Larry's potential life span, but it would seem to me that he is doing okay. Personally, I don't want to see Larry sacrificing quality of life in pursuit of what Bernstein, et al have set as the "perfect profile." Seeking perfection can, and usually does, lead to burnout.
Larry, you are doing great! Keep up the good work and don't worry about being perfect. A lot of what you are finding may simply be your age. If you can manage to keep your HbA1c levels where they are, or perhaps a bit lower, you will do fine. Remeber that "the enemy of better is 'BEST!'"