I would keep treating him with Reptile Relief until you get the PAM in. Once you get it in soak the snake, and treat him with the Reptile Relief, then clean EVERYTHING in his enviroment and then treat it with PAM.
After the PAM dries put him back in his setup and in 2 weeks repeat. I had a really bad mite investation that was brought into my collection because of a new addition a little over a year ago, I did exactly what I just told you to do and I haven't had a single mite problem since.