Carpetride,
I can only answer your first question.
I only use the rib hooks for up to six full spare ribs, but more will fit. I hook the hooks between the second and third rib bones, but if the rack is very long, place the hook between the third and fourth rib bones. I bought three of the special rib racks and I don't like them. The rib hooks always smokes the ribs as I prefer.
I don't use the probe with ribs, only check the ribs after five hours and when the ribs have receded up the bone about 1/2 to 3/4 of an inch they are done. Also, a little twist of the bones with the meat coming loose is a good sign of ready to eat. I always use a slather as I remove the ribs from the AmeriQue. I like a fruit juice, maple syrup and red pepper slather. Other methods will work just as well as the AmeriQue is very forgiving.