Can you use exercise to calm a dog?
It would actually be a good idea to start by trying that.
Dogs without exercise and mental stimulation are more likely to suffer from anxiety.
Be sure to give your dog plenty of energy when driving for five hours straight with him in the backseat.
Walk him for as long as you can have him run around a bit and play a game of fetch before you put him in the car.
Donot forget to give him a nice chew toy to keep him occupied.