I tow a 2507 lb. dry weight, 7 ft. wide TT, with a WDH and sway control, as well as a brake controller. I wouldn't tow much more with my 2010 Pathfinder with a 6000 lb. tow capacity - maybe up to 3000 lb., as long as the TT isn't more than 7 feet wide. With my set up, I get around 11.5-12.5 mpg. My Pathfinder is beefier than your redesigned Pathfinder - it's built on the Frontier truck chassis, whereas yours is now on a crossover chassis. I wouldn't tow 3700 lb. with my SUV, especially if the TT was 8 ft. wide, so I definitely wouldn't tow it with yours. You have to consider the frontal area, as well as the length and weight of the TT.
I can tow my TT at 60 mph with rpms around 2250-2500, if it's not too hilly. RPMs spike to around 3500 on hills, again, keeping my speed around 55-60 mph. If I punch it too hard going up a hill, the rpms will go even higher, so I usually let my speed drop to 55 on hills.