It took me a few hours with a hammer and chisel to force remove these clinkers.
Heres what it looked like when I first opened it up. You can see that more heat was at the center of the chamber. It was cooler th the edges. Well over 2000 in the middle. Maybe 1800 by the walls.
I do like the wood glazing that occurred on the bricks. The cracking and tearing is most likely from the rapid heating of the clay in the bricks. Need to slow it down to at least double the time on firing. At least 8 to 10 hours. And max temp no more than 1850'F.