A itinerary for a trip of a life time. You pretty named all the countries there are. I hope your car is 4x4. As for the film I would not depend on running a fridge in the back, you might be better off with a highly insulated 7 day cooler. A constant temp is better than cooling an warming everytime you turn off the car. Warm temps as long as well shielded from direct sunlight should be fine.
You can do a test to see just Incase. Shoot 3 rolls, one to leave in house, other to bake in car, last to stay in thick cooler. Wait like a week or two and see what damage it has caused. Try a faster film speed to judge damage. There honestly might not be a big difference or a perceivable difference at all.
Such as the one shot cameras people used to leave in the car for accidents for years on end baking, they usually held up fine.