ok, so i cant comment on the pentastar engine adn how well it will tow, but i can give in a little insite on the wheel base thing.
my old 4runner is about the same WB as the JKU is, i think the JK might be a touch longer. and with that 4runner on several occasions, i towed a 19 foot Momba ski boat. tracked straight and handled very well. so you should be fine in that category.
not to mention, my 4runner had about 100 HP less then the new pentastar, and i though it did ok with the weight, so i dont see why the JKU would have an issue, sure, not as good as a big V8, but not bad either.