The '85 T-1661 is rated at 195# hitch weight and a GVWR of 2,000#. That is way lighter than a lot of boats.
Tongue weight should be up around 12% of the traveling weight of the trailer so even if you take it up to 250# or a bit more, you are still well within the ratings for your receiver.
I am presuming that your shank, ball platform, and ball all have similar ratings to your receiver. If one of them is really low, consider replacing it with something more in line with the other parts.
As for sway control, you might consider adding a single friction unit. They are fairly inexpensive, and the needed tab and ball can be welded onto most existing ball platforms. Even if you didn't experience sway on your first tow, it can show itself later on. It's one of those things that you may not need all the time but when you do, if it isn't there, then it is a real problem. You are already thinking about how to add it so...
I've towed a lot of different trailers over the years, and I don't see the need for a weight distribution system given the size of your tow vehicle as long as the rig sits fairly level when fully loaded and ready to travel. If 200 plus pounds of tongue weight causes the rear of the truck to sag, then weight distribution is advisable, but I don't think you'll see that with the Durango.
You've actually got a real strong tow vehicle there. Presuming it has the HD cooling and such, it could well tow a much larger trailer.
One other thing you'll want to be sure to have is a decent brake controller in the truck and properly adjusted for the rig. There are a number of threads already here about fine tuning brake controllers.
Our good friend Norm Millard and his wife Ginny towed a 1550 all over North America with a Honda CRV with no issues. He didn't have a WD setup but carefully loaded the trailer and car. Got pretty good gas mileage, too as I recall.
Oh yeah, if you decide to go for a WD system somewhere down the road, I have a deep drop 2" shank sitting here waiting for a good home... :^)