Ok, I just talked to my local Toyota Dealer, which has a pretty good reputation in the area for being honest and doing right by the customer (I say this because so many places I've read hold them in about the same esteem as a congressperson
) and the gent said that as long as the trailer was "close" to 5000lbs it would be fine, as Toyota puts a certain fudge factor in there. He said even 400-500lbs over would be acceptable, although at high speeds or climbing mountains it might have to work harder.
I was pretty clear that the weight of the trailer and the stuff inside would be pretty darn close to the 5000lb and asked if there would be any safety concerns or additional wear on the engine. "no, because that's the tolerance Toyota builds into the vehicle. Anything more, and it could put a strain on the engine".
So now, following my rollercoaster of emotions, my thinking is that if I add air bags to stiffen up the back end, and have the Anderson hitch, and prudently drive (I'm not a lead foot anyway, but don't see the need of limiting the speed to below the speed limit) I just might be able to get it back to Maine from BC and will also be able to assess the tow ability of the trailer with the FJ. Plus, after that epic road trip, we will be broke for a while and might just driveway camp!