I'd get the alignment on the Fit checked.
I have a 2010 Fit Sport with 93,000 miles on it. Just got the 3rd set of tires for it. I'm averaging 45,000 miles per set, rotating the tires every 10k. I've towed it on a dolly a couple of times, but didn't notice anything special about tire wear.
I do agree with watching the driving technique on the RV as the large overhangs really exaggerate movement of the toad. Still, an alignment on the Fit would be the very first thing I would try. Take it to a reputable shop, not necessarily a chain store unless they know that chain store does really good work.