After a little research, I noticed the 2008 Highlander is a new model, maybe why Trailer Life showed the 08 as 3,500 max, and the 09 5,000 max. In any case, I did notice several sources agreeing with your figure of 5,000 lb max tow on the 08 with all proper equipment installed.
I think this vehicle will work with your trailer, if used under ideal towing conditions, at reasonable speed. I would not expect it to hold up to long term towing, especially in not so ideal situations, such as up steep hills, or towing higher speeds against the wind.
Enjoy the new trailer, and puppy! I hope the Highlander works for you, but not the ideal tool for the job.
Jerry
