Looks like all your numbers are good, I would expect the towing experience to be better if you were closer to 15% TW, but that's too much for the hitch you have.
I do recommend reweighing the TH as often feasible, it's amazing how the weight adds up without thinking anything else is in the trailer.
With a trailer that size the HA may not be the best choice, and something that allows you 15% TW would probably do better.
I guess the weight of the hitch being subtracted doesn't make any sense to me. The hitch is designed to support 1400lb of TW, regardless of how it gets there.
