Aren't we in the off-road forum? I had heard of airing down. Over the last few months, I've received quite an education.
Net: the load rating is not just a load but includes other parameters such as speed. The Toyo chart, available as a complete booklet, will give the load capacity vs. pressure for each size. LT tires have a safety margin built-in. Non-LT need to have the load reduced by 10% to be equivalent.
Initially, I was told people air down to 20-25psi and maybe 15psi on beaches. More recently I seeing 10psi or lower not being uncommon. That isn't for sustained highway driving. But driving over sand, trails, rocks, etc. The deformed tire has much more grip. Not in cornering, but in going through sand and over rough terrain. 17" rims (which won't fit a Ram 1500) are popular because they have taller sidewalls that allow more deformation. Taller tires not only add ground clearance, especially under the live axle differential but allow yet more deformation. AEV sells a 3" lift and fender flares for a RAM 2500 that allow 40" tires.
Off-road tires not only have stronger sidewalls, but they also have tread blocks on the sidewalls and deeper tread.
On the other side, dually owners often run under 50lb in the rear tires when not towing. Under load, that is raised to 65-80psi. 80psi unloaded just bounces around.
Matt's Towing is a popular YouTube site with 60k subscribers and around 150k view/video. He modified his truck to have a 4-bar rear suspension (just like a Ram 1500) and uses 35/12.5-17 tires (currently Milestar Patagonia M/Ts) at under 10psi.