I would say the dealer is not prepping the part right. Though I have seen very commonly that that area of paint gets so hot that it does that. I have a mustang in my shop right now, that is doing exactly that. Its gotta be from the heat.
As for your spray paint question, it means allow 7 days to cure before adding a top coat. Once its dried its okay to use it. I would have to say it will cure in these tempuratures at a faster rate then 7 days.
I have some viper blue I believe in the shop right now if its painted to match. I would be willing to give it a shot for you.