Hi Janine, I am sorry to hear of your dilemma..Yes I would suggest a second opinion either at Toyota or another reliable mechanic.
It is rare to have a CVT failure at such low mileage but it can happen.
As you said it had not had a good service history it could be that the transmission had a tough life either towing or driven hard.
Please update us on what the outcome of the second opinion turns out too be, if it requires a replacement transmission someone may have a source or advise where to locate one for a good quality replacement unit.
KAA