I have a larger tow vehicle, slightly longer but lighter TT, and the same hitch. My TW is ~850-900 lbs depending on tanks and such. I get pushed around when trucks pass, and you'll find that most folks with TTs do at least a little. As long as the push incident of the passing vehicle doesn't cause you to start oscillating then your hitch is working fine.
I found increasing TW made for a better tow in my case, but your receiver is already overloaded. Load E tires might help... Maybe heavier duty shocks?
