Controlling the temps is truly the issue. I'm new to WSMs and as you, just got my 22. I've been struggling a bit, trying to keep temps in the 225 to 250 range. My door is the same as yours is, even though I've attempted to bend it to conform to the opening. Seems every adjustment I make causes the metal to deform in another area, so for now, I've given up. I also just ordered the CB door with hopes that it will solve the issue.
Also, measure the bottom of the center section for roundness. Mine was out by a quarter inch and with a simple adjustment, I trued it up. After that, for the first time, I was able to kill the coals in a 1/2 hour by closing the vents. Before this, my coals would go on for hours and hours.