1) Totally dog dependent. My boy is fine in the car. He is used to us traveling all over the place for shows, training exercises etc. He can easily do full days in the car no problem. Make your plans flexible. If your dog just can't handle being in the car, take a break, or stop for the day if possible. It really is just dog dependent. We travel a lot and I know what he's capable of. Of course, when we stop, I find a field I can run him out in just to give him the opportunity to get rid of any energy he wants to get rid of.
2) Again dog dependent. Usually, I don't really deviate from his regular schedule. I feed him at the same times, I give him water, and stick to his daily bathroom schedule. I have a truck with air vents in the ceiling and seperate temperature control zones in the rear of the truck. Before we leave for a long trip, I fold all the seats down (they fold flat). I put his bed, and a big blanket down. He likes to be closer to us on long trips instead of way back in the trunk. I pack our stuff all around him so he has a cozy area to lay down. I angle the ceiling vents towards him. He loves AC blowing on him. He goes right to sleep for the majority of our car trips.
3) I can't really offer advice for this, as my dog is totally comfortable in the car. All I can say is a dog that is bouncing around in the car is extremely dangerous. You may want to consider crating during transport if this is the case.
If you are leaving her for long periods alone, you may want to transition her slowly. Do you crate her? If you don't crate her, I wouldn't give her full reign of the house without giving her time to adjust to the new place.