With or without a weight distribution hitch you can only tow the amount of weight that your vehicle is safely rated to tow.
Having a weight distribution hitch does not allow you to tow more than you vehicle is rated for so no you cannot increase your towing capacity with a weight distribution hitch.
The weight distribution hitch just distributes the trailers weight to help prevent sway and keep your vehicle from squatting as much which makes it safer for your vehicle to tow the RV or trailer.