Blue Ox owner here. Good advice so far. I too was sold 1000lb bars with my trailer and experienced what you describe. I weighed my tongue when loaded and was at 1350. Dealer wasn't a lot of help swapping for 1500lb bars so I called Blue Ox and they swapped them no problem.
You should be hooking the chains on the 9th link. You can go up another link or two if needed. Make sure you have a good strong tongue jack to take the load off the bars before unhooking, they will snap the provided wrench right out of your hand. That is why most of us use a socket and breaker bar. If the release lever is hard to release you need to lift the jack to take more weight off before you release the bars.
One more thing, if you have traction control control on your truck, they recommend turning it off as it fights with the anti sway properties of the hitch.