Permethrin that was applied and dried a week ago shouldn't be a problem. Permethrin poisoning symptoms are neurological, you would see stargazing and corkscrewing, not RI symptoms. It sounds more like your snake has an RI and needs to see a vet for antibiotics.

You said the hot side was at 92*F. What was the cool side? Also what is the humidity - if it's too hot and dry that may cause a regurge.