Mike you've just learned the sorry lesson of the "buy a snake get a free case of mites with every purchase" thing. Sadly it's far too common in pet stores and some less than reputable flippers or breeders.

Your snake is going to be stressed. The bathing, the upcoming P.A.M treatment, heck the mites themselves are likely making the snake uncomfortable. This is just what it is for now. Kind of like making your children take nasty needles because they need their vaccinations. Just deal with it as best you can then when it's all over and done with, start the settling in period over again. In other words, don't even count this difficult time as anything other than a crappy start to owning your snake.

Oh and just because I don't like to see pet stores get away with this. I'd take a nice sample of those mites off your snake into that store and show the owner/manager. Ask them if they usually sell infested animals and if they intend to cover the costs of treatment. They likely won't but they should know this is NOT an acceptable way to do business.