Towing Heavy with Goodyear DuraTrac

IME, they will handle the weight as well as any other tire of the same capacity.
I found, on the set I had in CO, lots of I70 western slope commuting, that the tread pattern on the Duratracs seemed to not hold up as well, cupped more on the outsides, compared to the BFG ATs and PRo Comp at and mt tires I had doing the same duty.
Can't get away from that completely in he mountains, driving exclusively twisty roads, but the Duras were not the best in this situation.
Had several sets of Duras on my fleet in Alaska and this did not happen but they were driven almost exclusively on ice and snow.

I run the same size with studs for the winter as well, I've had to tow my 5er around town for the suspension work and to the dealer for the free winterizing and tutorial(on this particular unit) and to my surprise the tires felt very solid and stable. That being said I wouldn't live with the noise during the summer months. Too many good much quieter AT's out there for much less money.

We had duratracs on our F250 and towed our 9K tt around the country for 6 months full timing. We liked them a lot and had no problems with them. So much so, they are now on our Jeep toad. We sold the truck when the tires had about 40K miles - more than half of them towing. We put them on because we spent our non-towing time off road in sand, dirt, mud, and snow. They worked well, especially considering the weight of the truck. They were louder on the highway than standard truck tires but with the diesel engine, you really didn't notice. If we didn't spend quite a bit of time off road, we would probably go with a cheaper road tire.

Deploying two sets of wheels is a great idea. Having said that I used one winter set and one all season for summer towing season.
Your going to see much less life span with those soft rubber tires in the summer heat IMO.

I use a second set of wheels in the winter with studs. For summer, I will use a different set of DuraTracks without studs.

Use with caution if they are studded as many states require studded tires be removed during the summer months. One place I worked at years ago had studded tires on a pickup and driving it on dry pavement was like driving on ice.