What a great tip this has been for me!
It was not easy, given the short clearance between the back wall and the square-drive screws that (since I could not really see them) appeared to be Phillips heads, but I figured it out and got the cover off. My greatest insight has been that my control knob was slipping some on the thermostat control rod. It's hard to describe, since it did catch with regularity at certain points, and slipped with regularity at others. Bottom line: my stove was going out below the 2 setting, and I observed that with a cold stove, at 2 the air intake was still closed. Now, the intake has a small hole in it so the air is never COMPLETELY cut off, but it was reduced enough to kill the fire. I had been rather gentle with the control nob, never forcing it beyond the low range of below 1 and the high range of 3 1/2. But I discovered that the knob is threaded and I was able to screw it down a full turn more, so no more slipping. By the way, the stove was a Craigslist find, so it is possible and plausible that someone UN-screwed the knob a full turn before I owned it. I'm going to be able to do a little fine-tuning, but where 2 used to be, I have now set at a little below 1.
Oh by the way, "it won't affect the burn or hurt anything (to take the cover off): when I did a hot reload, some smoke fed up the primary (low) air intake and out into the room, so I will leave the cover off for an observation period, but I sure as he ll am going to put it back on after a few burn cycles. Anyway, thank you, thank you, for the idea to do this most useful exercise.