Wouldn't you want to actually know what your weight limits are rather than guessing that everything seems OK?
If you add anything into the Sequoia, that adds to the total payload carried. Assuming that you are using a typical weight distributing hitch, your current cargo carried is 720 lbs. (tongue weight) + 80 lbs. (WDH) + 380 lbs. (your estimate) + weight of fuel (?) = 1180 lbs. + (?). The payload capacity rating for your vehicle is 1260 lbs.
The payload capacity is a number derived by the engineers and testing folks of the manufacturer of your vehicle. It is provided to the owner so they know what the vehicle is capable of safely handling without damage to the vehicle's suspension, frame, running gear, and occupants.
