First off new BP's should be left alone for a minimal for a week to settle in to their new environment, no touching~taking it out~handling, no trying to feed it, etc. It will only stress the snake out more.
Second off adult BP's don't need to eat a rat any larger then a small. A snake really shouldn't eat anything larger then it's widest girth size.
Third off please take your new snake to a herp vet, blowing bubbles and it spitting up are both major signs of a respiratory infection. If you do not know of a herp vet near you please state your location and we will try to find a herp vet near you.
As for the head wound, a triple antibiotic cream with out pain killer in it will do to help heal and fight off any infection. The vet can check it out when you take her in to get her checked out for a RI.
Last NEVER EVER feed a life rat to your snake by dangling it by it's tail. That's just going to piss it off and it's either going to fail around, bite you, or bite your snake.