Nice rig for sure. That is a monster. Maybe that's why the guy sold it. Maybe he found it was to big for him to handle.
I bought a 38' fiver with three big slides with load range G tires as I assume yours is. I got a feeling your weight is off a little bit and I think it is heavier. You should scale it, because my weight at the axles was around 14k with 3k on the hitch, fully loaded for a trip. I wouldn't feel comfortable with a 3/4 ton with single rear wheels pulling that.
I bought mine in 2002 and a Dmax Dually around the same time. No squishy ride at all. It drops the rear end about 2 inches if I recall, so all is good. It pulls it nice and is the a nice way to travel,,,as long as you have a nice landing spot. You can enjoy your home away from home, your own kitchen and your own bedroom.
We had a 3 year warranty so I used that for every little bitty thing as the dealership was very convenient. As long as you got your thing so cheap if you need to spend a little bit down the line it won't be a big deal.
After the warranty was done all I had to do in 15 years with 8 years of snowbirding was tires, and I replaced all the brakes. When I pulled them off 3 were still good but had one bad one but I changed them all anyway. And I replaced the LP regulator last week. Not bad for using it for living in almost full time for so long and I still use it for camping trips one week each month. I go with 6-8 couples but they are mostly high rollers with big class A motor homes.
Have fun camping.