A-Liner Sway

Do you need the 20 gallons fresh water? Maybe try buying 3 of the 7 gallon Aqua-Tainer water containers stored as far forward as you can and the fresh tank empty. Then fill the fresh tank from the Aqua-Tainers when you get to your destination.
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Tongue weight is to low. Needs to be 200+ lbs. Air the A liners tires up to the max on the sidewall.
You should be able to rip down the hwy at 70 without concern providing the A's tires are up to it.

And what you’re describing that you’re experiencing isn’t “trailer sway” in the true sense of the definition. Although a little more tongue weight would help.
I couldnt imagine installing sway control on a little ole trailer like that being towed with a vehicle that large and capable compared to the size of the trailer.
First question is ask yourself what your basis for comparison is. IE how much towing experience you have or don’t have. Semis and cross winds push cars and light trucks with trailers around. Whether what you’re experiencing is excessive or normal is subjective.
But the tongue is a bit light. Is it better with no water? Try some extra weight forward to increase the tongue weight. However you can effect that.

Sway controls are a poor band aid fix for lack of proper tongue weight. Trailers need a minimum of 10% of total weight on the tongue to track properly.

Google Friction Sway Control.

You need about 250 pound tongue weight. 15% or 300 pounds would be even better.

Thanks! Been trying to get 60% front of the axle but not sure how to measure? Interestingly, A-Liner has the 20 gallon water tank (160 lbs) aft of the axle.

Put more weight closer to the front.