I read the book I mentioned in the original post on this thread, which was very helpful and gave me the confidence to give it a try.

When resuming the niacin I had flushes for like a week, but now it's back to normal: take it with meals, no flushing, and feel good.

Also dug around a little, and just like when I was researching female hormones to help with menopause, papers don't seem to distinguish between Progestin (which is manipulated for patent purposes and has dangerous side effects) and progesterone, which is biologically identical and has very very few.

So it turns out, a lot of these papers that have been spooking me about "niacin" triggering insulin resistance and the like are similarly sloppy about distinguishing between slow-release, no-flush, niacinamide, jerked around prescription versions, and actual basic niacin, which is what I take.

Worry averted. I will keep calm and carry on. If anything, this regimen makes me crave food I'm supposed to be eating. Which is amazing by any measure. And indicates great blood sugar control.