Dave, I've got an opinion on your vent adjustment question.
On one of my first really long cooks (14-15 hours), I did almost all of the temp adjusting by opening just one vent. During the late hours of the cook, it got harder to maintain my temps and I went to stir the coals/add charcoal and noticed that I had a crescent moon shaped ring of charcoal left. The fire had clearly burned hotter near the open vent and moved across the charcoal pile. It got harder to keep temps up the farther the fire got from the vent I was using.
I ended up having to do a lot more work with charcoal stirring, etc than I have done in my long cooks since that time as I have tried to adjust each vent evenly since then. The fire seems to burn more evenly and is more efficient in using all of the available charcoal without having to add more.