receivers and ball size for 7000lb GVWR trailer

Full height bumper pull trailers tend to tow comfortably with 13-15% TW vs. closer to 10%. 7000 pounds of loaded weight means means 900-1000 pounds of TW. In my experience towing with a half ton, a WDH provides noticeable benefits when towing over about 4000 pounds of TT weight. Check your receiver for tongue weight limits without a WDH. I think you need a WDH to tow that weight, which generally come with an adjustable height ball mount.