Generally the cost will depend on the variant and year. You can get more information on quick and cheap key replacments from dealers or automotive locksmiths here.

You’ve pretty much covered the field there, so it should come down to what you want from your car. Do you want comfort, safety, fuel efficiency, offroad capability, cabin space? If you are mostly driving on the highway, then a diesel SUV is probably the best bet. I would rule out a dual-cab ute because of comfort, unless you need the flexibility a ute gives you. I would rule out a hybrid, they’re not at their most efficient on the highway; they’re better suited to town use. Based on your annual mileage I wouldn’t keep the car any more than 3-4 years, that way you’ll have a decent resale value when you get out of it.

The diesel is fine around town. Being just three years old there shouldn't be anything wrong, so apart from overall condition of the body, paint, and interior make sure it has been routinely serviced.