mtofell is spot on, and one of the better towing advisors here. OP I'd listen to him if I asked for advice and he responded.
OP what mtofell is trying to tell you, is that your truck has a white and yellow sticker inside the door jamb of your driver's front door. It lists the GVWR of your truck, what your payload is, and usually what your axle ratings are. THESE numbers mean more than anything you'll look up online for your truck. And depending on the 1500, we have heard of payloads as low as 900 lbs and as high as 2k+ (usually regular cab long box 2wd work trucks - definitely NOT what you have). If I had to guess, I would say your payload is lower than most, probably in the 1100-1200 range but without the info on your door jamb I'm guessing.
If your truck is truly rated to tow 10k lbs, you'll only get there by towing an equipment trailer with the load almost entirely centered over the axles so the trailer is taking all the weight. You're probably overweight with your current setup.
The truck's physical limitations will run out LONG before you get a travel trailer close to that weight behind you. A 6800 lb travel trailer will have somewhere around 680-750 lbs of tongue weight (possibly more depending on layout). That's a LOT of weight on your truck, and IF you're going to go with this you're going to NEED (not want) a weight distribution hitch and sway control, either separate (how I run) or a combo unit (many will suggest an Anderson or Huky Straightline or something along those lines). Your problem is going to be compounded by the fact that WDH systems don't really play nice with air suspension, so there's a different process you have to run through to set it up properly.
As for converting between coils or upgrading your bags (if it is possible), you are still likely going to be near the limits of your truck either way. Yes, going to coils will make the rear sag more than with your air suspension, your air suspension is probably working REALLY hard to keep your truck level. The thing to remember about coils, factory or otherwise, is that they're variable rate - the more weight you put on them, the higher their spring rate becomes. So as you start to load them up they compress quickly up to a point, then that compression slows down. So even if it looks like it's sagging after hooking up and setting up your WDH, it might actually be where it needs to be, if you've got the weight back on your front axle and back on the trailer's axles.
Hope this makes some sense - it's early, I haven't had coffee yet, and I'm just going off the cuff, I'm sure I've missed some things here and there.