You did not say if your truck has airbags that automatically keep the truck level (airing up when trailer is dropped on hitch).
If it levels itself then you do not need a WD hitch to help level.
If you are within the weight limit then you do not need a WD hitch.
The Ram manual is not talking about weights with using WD hitch unless it specifically states weights using a WD hitch.
A WD hitch will typically give a smoother ride and prevent the dolphin effect. A more comfy ride.
If your 7,000 gross weight trailer is loaded out to 7,000 lbs then your tongue weight should be 10-15% of that, 700-1,200 lbs or so. This is well under the rated 1,800 lbs your truck is designed for, so again, no you do not need a WD hitch necessarily. WD hitch would be for other benefits, not for tongue weight.