Sounds like the Pacifica performed as designed. The Pontoon boat in the pictures creates a lot of air drag.The 3.6 Pentatstar does not start making good power and torque till around 3000 rpm. Torque peak is around 4200 Rpm. When I tow a 6x12 enclosed utility trailer, with my 2015 Caravan, I can hold 5th (2500-2600 rpms) on the straight and level, but hilly country requires running in fourth (3100- 3500 rpms). I tow 3000 lbs all day long at 3100 - 3500 rpms.
Foot Note: I towed a 6000# 7x14 Haulmark enclosed trailer with 2012 Dodge Durango with 3.6 pentastar and Mercedes 5 speed trans. Same story as our vans, needed to run around 3000-3500 rpms. I towed mostly in 3rd gear. 4th would pull engine rpms down to 2500 rpm and any kind of hill, or wind, would force a downshift. I stayed in 3rd all the time, to prevent constant shifting. I towed that combo for two years, and many thousands of miles. Nothing every got too hot, and we averaged 9 mpg.