Sounds about right. Never weighed my AF 860 but just calculating the amount of airbag pressure vs surface area to get the ride height back to stock I was coming in at 4k to 4500lbs for the loaded camper.
I've been running Toyo MTs on my Dodge. 3950lb load rating. Tread life is horrible but expected since I siped the tires as well (before buying the camper).
That said those tires held up well to a trip up the Alcan Hwy towing a size able trailer as well and many trips around AK with a lot of frost heaves and gravel/rocks.
Without going to 19.5s I'd get the Toyos again but not in a MT.