I think with a 2500 you might actually have a little more room to play with but I am not sure what the load limit is on the 3/4 ton. They usually recommend the tongue weight being no more than 10 % of the max load
You're right it's at least 500. Truck is a 2500 w tow pkg so its got the III or IV class hitch, can't remember. I just didn't want to quote a number up there and it be off. I'll look next time I'm laying on the floor.