The tyre pressures are best set to the manufacturer’s recommended pressures, bearing in mind that you need to adjust your pressures according to the load you’re carrying in your ute. You can run the pressures a little higher than recommended, if you like, and generally you will reduce your fuel consumption, and improve your handling and braking, but at the cost of ride comfort. But running them at 40 psi as the tyre retailer has recommended is too high, you’d want to know a good dentist if you ran them that high. As for the wear, check your alignment and make sure that is correct.