GVWR, AXLE Ratings, and Tire Load Range???

I need to check and see if I can find specs on these wheels to see if they are rated at 80psi. Wheel manufacturer may or may not be in business? I don't recall ever seeing psi rating stamped on wheels...only the rim size.

I never saw a 16" trailer wheel that was rated less than 80 psi.
Your ST235/80-16 D tires must be old ....however that was a common size/load range several year back before 16" ST E hit the tire stores.
Those 16" wheels will have a load rating which may be good for 3000 up to 3500 lbs. Those wheels will be good at 80 psi.

Don't forget about a 16" LT235/85-16 E or LT245/75-16 E both at 3042 lbs capacity if the trailer has room in the wheel well. Their good for 12168 lb gross axle weight.
A all steel ply carcass commercial grade Bridgestone R-250 will give you years of trouble free service. Check them out.