As for the charcoal load question, they do recommend using a full basket (8 lbs) for each cook. However, as you get used to cook times you can "cheat" by adjusting according to the load and the maximal cook time. For example, tri-tip takes only 35 minutes, so I use about half a basket. Chicken halves take about two hours, so if I'm only cooking a few (four or less halves) I'll use about 2/3 of a basket.
All that said, I HIGHLY recommend starting out with a full basket for each cook. Again, once you get a good feel for it then start to color outside the lines.
I hope this helps.