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"payload" rating is close enough which includes any passengers. I don't think the "options" can add up to much. 3rd row seats weigh about 80 lbs though (removed mine and weighed for curiosity) and rear hvac may add a few so you could assign 100ish lbs to those.
I'd also think the safety aspect has more to do with speed up to a point. Rolling 50 mph on side roads you could "safely" haul a lot more lbs than 80 mph down the interstate in the event of an unplanned interaction with animal, other vehicle or bad road conditions.