I don't drive for Uber, but have used it a few times.
1. You don't have to put in your destination when you request a pick up. Most people do though.
2. You can cancel if you don't want to go to that area. I had a guy do that the other night and he said he was cancelling because we wanted to finish up and wasn't going my way.
3. Probably not. I've spoken to drivers before and they say they can make $25-$30 per hour. I highly doubt they take into account wear and tear, dead time, gas, insurance etc. My last trip was $16, it was a 12 min trip, but took the guy a few mins to get to me. Then he has to drive around looking for another. I had one guy, 6 minute trip was $10. Not too bad!!..except it took him 15 mins to get to me and finally find me because the app said I was on a different road.
If you do busy nights you probably could get job after job. Just have to weigh your social life. It wouldn't be bad to do I guess if you drove a lot and were just going to pick people up to help with the fare.