renojack, with as heavy as your trailer is I would try using atleast 1/4" of compression of the bushings which was roughly 9 threads. With only 7 thread you aren't getting anywhere near enough compression on the bushings to transfer the weight.
On my F150/Grey Wolf 26BH combo (with 650-700lb tongue weight), compressing the bushings 1/4" raised the rear of my truck to with-in about 1/4-3/8" of the unloaded height and dropped the front end 1/8" from the unloaded height. I don't have a scale locally, but just by taking measurements it is quiet evident that the hitch did transfer a good amount of weight on my truck.
Instead of counting threads I always measure the bushing. To me its a lot more accurate way of getting the same tension and WD with this hitch.