We've boondocked all over Utah and *knocks on wood* haven't gotten stuck in sand here yet. On the way to our current site, there is several hundred feet of soft sand that I sink down a couple inches in, when walking on it. 4H is usually more than sufficient for small bouts of sand, 4L is more useful when you need granular control for crawling over rocks. If you have at least a rear locker, that'll help a lot.
One of our friends got stuck nearby with a semi tractor pulling a fifth wheel, but their drive tires aren't well suited for off road and they had probably 12K plus whatever the truck itself adds on the rear axles.
We alternate between a fifth wheel and truck camper, both of which are much heavier than your rig. Take traction mats and don't worry about it.
We never air down unless we're talking about the Jeep, and only then for specific trails.
