IMO, that price seems a little high for late in the season sale. Have you checked to make sure its been well maintained and is leak free? Any signs of water intrusion are bad for a trailer. I would make sure the caulking on the roof is in good shape meaning the previous owners kept on it.
I have a similar TV to yours (Traverse), but my 18SB is about 800lbs less. Mine tows ok and I have never felt unsafe but it could use more low end power.
I think you will be very close to maxed out in every weight with that trailer and TV. You will need to be very careful in how much stuff you bring along. It will probably be ok on lower speed roads, but it will not be too fun on hilly interstate. I would plan on a larger TV in the near future and I wouldn't plan any real long trips.