2 of the "exposed lug nuts" 180* from each other should have a horizontal slash across the wrench lands. Those nuts need to be removed with the T wrench to remove the hub cap.
As for the "Tow/Haul" button (5 and 6 speed transmissions) it changes the shift points, but still allows the transmission to go into overdrive. The "OD" button on the 4 speed (4R100) does lock out overdrive.
An additional feature of the 5 and 6 speed transmissions is when the Tow/Haul mode is engaged it will also provide engine braking. To slow the vehicle when going down hill with Tow/Haul engaged depress the brake pedal for 1 second or longer. If the speed increases more than 3 mph the transmission will downshift to the next lower gear if is within ithe safe RPM range.
Cruise control will perform a similar function. If going down hill with the cruise engaged it will downshift to the next lower gear maintain the set speed if it's within the safe RPM range.