How much can this truck REALLY tow?

First, don't buy a trailer that has wood in its construction. Second with a small turbo diesel you can run in 70% 80% of your rated capacity if you have good distribution. I use Andersen WD. Try and keep frontal surface down for your smaller truck. 7.5 ft in width. Look at the camplite 21 RBS or bunk. They have reduced the durability over the past few years but just checked and still no wood.

https://www.livinlite.com/products/camplite-travel-trailers/CL21BHS.html