1. havent tested yet
2. It feels like it depends on what iam cooking but usually i throw 8 pieces of firewood in there and its done when i come back
3. I calcinated half a stack and if i remeber correctly it used about 20 charcoal
4. About 750° C, but no matter what fuel you use you are gonna need bellows if you want to smith longer than 5 seconds. You can get the crude bellows very early thou.