Once you have the Bronco on the trailer and with some tongue weight, block the trailer tires and put the scale under the jack and unhook the trailer. I've read your posts three times and still not sure if you have a scale for weighing the tongue weight. Level the trailer and see what it weighs.
If you do not have a scale, then load the Bronco and when it lowers the back of your Dodge 2-3" tie it down. Put the WD bars on and bring it back up to level. Go out on a deserted road and at 45 MPH give the steering wheel a wiggle. If the trailer stops swaying on it's own without having to put the trailer brakes on to stop it... give the steering wheel a harder back and forth. If all is well then mark where the Bronco is on the trailer for future reference.
I haul all kind of equipment on various trailer with various TV and the wiggle test at 45 is all I ever do to see if I have enough tongue weight. I would start with the Bronco centered over the trailer's axles as the weight of the engine should give you minimum tongue weight that you are trying to get because of your overloaded situation with the long extension hitch.
