Tell your friend if he wants the snake to live, take it to a vet, if your friends doesn't care one way or the other, then try all the at home "remedies" you want. IMO you are well past curing the infection just by raising the temps.

As for the F10 you mentioned, I know there are videos on youtube from breeders that use it. I'm personally not sold on it. No where does it say it cures respiratory infections, it does say it kills viruses like parvo, but nothing about infections. Infections can get into the blood stream, no fogger can cure that. F10 is marketed as a disinfectant to sterilize tubs/rooms/etc. One of the meds commonly prescribed for RIs in snakes is the exact same med humans get for respiratory infections and blood poisoning. I'm wondering if F10 is more of a band-aid than a cure since serious infections need antibiotics. I could be totally wrong, but I will keep using prescribed medications until I get some serious proof that a disinfectant is better for treating RI's than antibiotics.