Over weight truck camper suspension upgrade needed

I think its the airbags and tires. Both will compound rocking and swaying. Steel springs may stiffen things somewhat but the rebound tendency will still be there, and each time you hit a rut, the tendency will be compounded.

The problem is not lifting the load its keeping the wild bronco in control.

Get some strong shocks as your shop recommended. See how that works. The 19.5 inch tires would be a good second option.