Just in case anyone is hanging on the edge of their seats:
I spoke with numerous potters; no one was willing/able to help me. So I gave it a go alone again.
The temperature stopped rising at 2175 (an additional two tanks and new regulator gave me 200 degrees! Woo!) - I held there for quite a bit, then shut it down. I reached anywhere from Cone 4 to Cone 6. Still that same flame that just goes through one shelf and out the flue. Still only one shelf with any reduction. I used twice the amount of soda as I had in the past (2 kg in this 19 cu ft kiln), and there's really no evidence of having added more than before. I believe the majority of it is going up the chimney (which, at that point, is less than 1" open at the damper).
In any event. This system, I believe, is fried. Done. The amount of heat radiating from the two burners - and the gauges just behind them - is absurd. I can't fathom the inter-workings to be still functioning properly. (The heat in the burners is almost immediate upon lighting, as that blue flame is in the throat [but not to the orifice].)
Currently in the Frustrated stage, scheming about building a wood kiln.