Weight vs. tire inflation can have a big impact on the quality of your ride. . Here's a good start:
RV Tire Safety: Cold Inflation
The author, Roger Marble, is a retired tire engineer who also posts on Winnieowners and IRV2 as Tireman9. There are a lot of posts about inflation that aren't necessarily accurate but Tireman9 knows his stuff.
I wouldn't jump to the sway bar or other suspension mods until you've dialed in your tire pressures and dealt with the shocks if they are indeed shot, although I wouldn't think a 2015 rig would need new shocks.