Doing the following may or may not matter but IMO, its worth trying, its free.
If you have been running your tires at max PSI , then I would air down the tires 5 lbs below max and try it.
Airing down 5 lbs is not going to hurt you or make the tire blow up, whether its a 50# or 65# rated tire.
I'm not overloaded , I run all my trailers 5 lbs below , been doing that for , I can't remember because it's been so long, ..... since 1969 .
Weigh your trailer, its sounds like you might have too much axle below it, making the ride stiff. Google torsion axles, many 'youtube videos', some can be adjusted but I don't know anything about that.
Google CAT scale locations near you or try sanitation centers, gravel yards and logging stations. Your state P.D. or DOT might help you as well. If so , bring enough coffee for everyone.