Great cook! I will let the brisket pros comment on what might have been the deal with the brisket, looks good though. My guess is that is needed more time.
As far as the temp swings on your pit let me tell you a story of my experience. When I got my jambo I wanted to know what the temps were at different points in the pit and had digital probes and wires running everywhere. To me, it was way to complicated and I stopped using everything except the thermo on the pit. You will eventually learn where your hot and cold spots are and can adjust meat placement accordingly without getting tangled up in wires. Once you learn the fire management part of the equation (which it looks like you have a good start on) you will realize that you will enjoy cooking more when you simplify. Stick burning is very rewarding and I enjoy it even more without the probes and wires.
This was my experience and it may or not be the way you want to go. If you are a tech guy that loves fiddling with digital equipment than by all means go for it. Either way, you are doing good so far, keep it up.
Jambo Backyard (Trailer Mounted)- The Quenivor
I don't use electronic gadgets while cooking for the same reason Ronnie Van Zant didn't wear shoes on stage.