You're doing great with the suggestions and your current plans. I never understood the "tie your dog to the bed of the truck" concept - a sudden stop and you can break the dog's neck from the pull of the rope. A good airline plastic crate, properly attached to the truck (if this will be a common travel situation, you might want to actually bolt the crate in, and possibly put an insulating layer of wood between the base of the crate and the metal of the truck bed) is the best.
For the ice in the bowl - fill the bowl with water, then stick it in the freezer. This can help keep the ice in the bowl longer. For longer trips, have an extra bowl in your ice chest filled and frozen to switch out halfway through.
If you have a sliding window in the cab of the truck, you can use that to stay in contact with the dog during the drive. A camper shell over the truck bed can provide more protection from wet weather, but can make it worse in hot weather.