I agree.
It sounds like the place where you bought it is trying to wash its hands of you already by saying any additional repairs are on your dime.

As others have said, it is the first model year which had many gremlins. It is 7yrs old, you don't know the service history or the background of the car and you don't have a warranty and there are already undiagnosed problems.

Maybe I am overreacting but I would be very nervous. You could ask your local dealership to run the VIN # to see if routine maintenance was performed an if there were any recurring problems.
But seeing as tomorrow is the last day that you can return it you don't have much time.
I would give it back and spend time looking for a newer model.

Good luck