If you add back in the 200 lbs for the 5er hitch, that leaves you with 1150 available payload, plenty to handle the tongue weight of just about any 30' travel trailer. 5ers usually put 20% on the pin and TTs put 12-13% on the tongue, so would likely be able to tow a bigger TT than a 5er.
As Jimlin pointed out you can likely stretch that with higher-rated tires and possibly air bags or Timbrens on the rear.
To answer your question, your numbers look right, and good thing you are doing the math now rather than after the RV salesman sells you that big honkin' trailer.....
You'll be able to get a nice rig that's bigger than a hybrid or pop-up, you just need to keep a close eye on the numbers.
On a final note, pay attention to the loaded weight of any trailer. On average you will add 1000-1500 lbs of stuff to either a 5er or TT, so be sure to add that to the dry weight of whatever trailer you are looking at. Most of the 5er's storage is in the basement up front, so a lot of that goes right to pin weight.