I’ll trade you my 860 for your 992. That should help with weight and center of load!
Seriously though, your truck is big enough, unless you expect it to drive like it does empty.
You have a 2 ton white whale on the back. And sounds like either your expectations aren’t in line with how it’s going to handle or you don’t understand why it’s acting the way it does.
It’s fine. Go camping. Yes overload springs will slap if their not engaged. EngAge them.
And if you can reasonably drove it around with very little help from air bags then you again don’t know how it should ride or it’s hauling the weight about as well as it should.