Weight distributing hitch

Your wdh does have adjustment for both the hitch height and the bar angle (see figures E and F on page 6 of the manual) so you should be able to get it set how you want. 

I really think that hitch will probably work fine for you.  The only thing that would change if you got a lighter duty wdh is the ride might be less stiff, which is a matter of personal preference. You own it already, why not get it set up and see what you think? 

As GlueGuy says, if you are getting sway, you first need to understand how you have the trailer loaded. Sway control is important to have but you don't want to have to depend on it to save you from a wreck due to an improperly loaded trailer. 

Check out this video:

If you're getting sway, you almost certainly have the trailer loaded too far aft. \

 Is there a public scale where you can weigh it nearby? I use the one at my local waste transfer station. Run through the scale with the fully loaded rig and without the wdh tensioned.  First get the weight of the tow vehicle only and then add the trailer axle to the scale and get the total rig weight. Then drop off the trailer and go weigh the tow vehicle by itself. The total rig weight minus the tow vehicle by itself is the trailer weight. The tow vehicle with trailer attached less the tow vehicle without the trailer is the tongue weight. 

If your tongue weight is less than about 11-12% of the trailer weight then you need to readjust your load.  The fresh water tank is forward of the axle in the 189. As a start, try filling it with water and drain the gray and black tanks.  Move anything heavy inside forward and/or try podwerk's trick of adding some water containers forward.  Then see if the sway goes away. It should. 

I would do any load weighing and readjustment before setting up the wdh as changing tongue weight will effect both the wdh setup and rig ride quality. 

All this sounds frustrating and complicated and it is the first time, but once you know what you have and get everything set up correctly you won't need to do it again unless you significantly change something, so it will be back to just enjoying camping.