1) 250-350 All depends on the time I have available.
2) I don't go by time, I go by texture and color. When I roast/smoke nuts, I want to remove the mealy texture and crisp the nuts. You have to remember, the nuts are going to crisp up some more as they cool. If you are using already roasted nuts, be careful. The point of being burnt and rancid, can be as as little as a minute or two, depending on temperature.
3) Any you prefer. I have used fruit(apple, cherry and peach), nut(almond and pecan), hickory and maple.
Another consideration, is the freshness of the nuts. Improperly stored and the nut oils will turn rancid in 30-45 days.