You called the manufacturer of the tires and they told you the correct information. If you don't want to weigh your rig running your tires at the max inflation value on the tire will not hurt anything other than your kidneys from the rough ride.
The door sticker only applies to the original tires that were on your truck. If you replace them with the exact same tires that door sticker will still apply. If you replace them with anything else go by the tire or the load/pressure table provided by that tire manufacturer.