A 4Runner is like any other mid-size SUV - you can pull a lot heavier trailer than you can handle the hitch weight of that trailer. You can either tow a nice travel trailer, or you can haul a load of people of stuff, but not both at the same time without exceeding the GVWR of your 4Runner.
Hit the CAT scale in the middle of your trip, with the trailer tied on and loaded to normal towing weight, with the spring bars of your WD hitch hooked up to normal tension, and with all your family and stuff in the 4Runner. Fill up with gas, then weigh the wet and loaded rig. Add the weights on the front and rear axle to get the GVW of the 4Runner. Compare the GVW to the GVWR of the 4Runner. Then and only then will you know whether your SUV is overloaded.
Grumpy ole man with over 50 years towing experience. Now my heaviest trailer is a 7,000-pound enclosed cargo trailer, RV is a 5,600 pound Skyline Nomad Joey 196S, and my tow vehicle is a 2012 F-150 EcoBoost SuperCrew.