Uh, check the max weight rating on those tires (should be embossed in the side). The rear axle has about 6,000 lbs sitting on it, so the tires need to be able to support that. The stock tires handle about 3,000 lbs at 80 psi - I don't know what the new ones have. I'm guessing they have enough capacity or you would've shredded one by now, though.
Definitely sounds like you have the steering issues resolved (or will soon). They're a top heavy vehicle, so it's going to feel a bit sloppy compared to a car, but at the same time it shouldn't be too much.
1995 Airstream Classic 30' Excella 1000
2014 Ram 2500 Crew Cab with Cummins 6.7L Diesel
Sold but not forgotten: 1991 Airstream B190
Sold: 2006 F-250 6.0L Powerstroke Supercab