We will pack light as possible but you are right- I may be close to maxing out the payload. I'm not sure if you are recommending the WD hitch or not though. If I do the WD hitch, the dealer recommendation is to make sure I put enough weight in the front of the trailer since the axle is very well centered and there isn't that much rear storage anyway.
I'm 175 lbs, the better half is probably 135, any the Shih Tzu is 20 lbs.
EDIT: When the 4Runner is calling it quits (or I suspect it is) I'll likely get a full-size pickup or a big SUV.