2. Do you have a copy of the owner's manual? If not, you can download a free copy from the Toyota.com website: 'Owners" tab, then 'Resources', then "Manuals and Warranties".
Most of the time, you'll be in 4th, but occasionally 3rd or even 2nd as necessary to allow a reasonable balance between throttle opening and RPM while climbing and while descending grades. 2WD ONLY on paved surfaces, but 4WD can be used for a few hundred feet straight ahead when pulling the boat out on a slippery ramp.
The short-wheelbase FJ was never intended to be a HD tow vehicle, hence no factory option with trans cooler, engine oil cooler, high-output alternator, etc. like is available on other Toyota trucks. If you are going to tow on anything other than dead flat, a transmission cooler and regular trans lubricant changes are highly recommended.
On long, moderately steep grades WITHOUT towing anything I occasionally saw torque converter outlet temperatures on my 2014 of over 240F before I added an auxiliary transmission cooler.