I guess when some one says a 4Runner can’t tow much, you have to look at it relatively. No, it can’t tow a flat bed with an excavator nor do you use it to tow a full size camper or a 40 foot sailboat. A dump truck does that and a 4Runner can’t compete in that range. But, for recreational towing of boats and campers in the 3 to 4k range, it is perfectly fine. The idea of running a big butt tow vehicle to commute with so you can tow these lighter loads is a waste of resources. 4k lbs range is right up the 6 cylinder tow alley for the 4Runner. Ahhh that’s one of the reasons why they are still made with a frame and a bouncy ( comparibly) ride. And 1500 lbs ? Why not.
Btw, the 4Runner that year comes standard with climate control. I run with it on all the time as the difference in driving an SUV at higher speeds has so much more influence on economy, it isn’t even worth talking about. Now, if this were a weak kneed Yaris, you might have a reason to turn if off…it just wouldn’t be enough what ever the reason.
Quite likely the issues of whether to run the A/C or not and fuel mileage will become moot points by the time you get into the rolling 100 degree wastelands of Nebraska and Kansas… 
Modern AC has very little effect on gas mileage, and at highway speeds is probably a wash. It will be completely undetectable compared to the hit you take from the trailer. Have a fun trip.