I am very concerned still, and I've read all the previous posts, and I don't know if you are taking us serious when we say the temps are still way too high. You say it's at 78 now, and you are getting the chin on Tuesday (from a not so good breeder as it sounds) Do you really think you can get the temp down to the mid 60's in 2 days without an A/C unit? I think that is impossible (or maybe not) even with the room pitch dark and "reflecting heat". It is currently 65 in my room where my chins are, and I am sitting here in a sweatshirt and socks and still shivering, but they are very happy and content. But if it was to my liking, around 75, they would be miserable, so chinnies before humans is the saying in this house, because it is for their safety.
And I agree with everyone else, please, please please call Tuesday off. You don't need to bring an animal that sensitive into a home where you are not 100% sure you can keep the temp constantly low. Just wait until you have your own place where you can control the temp and where you pay your own bills (There will still be plenty of chins that need good homes then).
I guess I'm just fortunate enough that I spend the summers at my parent's house, and they love it cold.