just remember that 5000lbs. is your FJ's max towing number.
you have to subtract any passengers(except the 150lb. driver) and cargo's weight in the FJ, from that number.
this will lower the prospective trailer's GVWR that you can tow.
it's always a good rule to have a tow vehicle that can tow the trailer's GVWR comfortably.
the FJ's high center of gravity and short wheelbase may also make towing a little more difficult, so you'll definitely need a good WDH with sway control.
i would look at a 19' TT or Hybrid to tow.
when we were shopping for a tow vehicle for our Roo 23SS, i really wanted a FJ or Xterra. but both of them have the same limitations for the trailer we wanted.