Definitely add in the cargo weight in the bed and passenger weight. The truck is a 1/2 ton so it's only designed for ~1000lb cargo and a driver. If you have two full-size people in the back seat and 500lb of trailer weight, you're already nearing that 1000lb. toss in a set of wheels & tires at 150lb and add more tools, and you're going to be past your truck's limit. Also keep in mind 500lb on the rear bumper is much harder on the rear suspension than 500lb directly over the rear axle.

I would suggest moving some of that stuff to the trailer. can you strap the tires & tools onto the trailer and move the car around to adjust the tongue weight?

I have a 3/4 ton F250 and a 24' enclosed, but I have all of my tools and spare tires in the nose of the trailer. the car gets strapped down with the rear bumper just clearing the door. drives great, albeit my truck is considerably larger than yours.
And that's just using a regular hitch, no sway control, weight distro hitch, etc. Get it balanced right and you can get rid of some of those bandaids.