My four month old puppy has demodectic mange?

I have a four month old boston terrier/chihuahua mix who was saved from a puppy mill when he was about 8 weeks old. I took him straight to the vet and he had a very bad case of Coccidia and worms. He was on Albon antibiotics for a month and a half (1 cc, 2x a day) and then was switched to Flagyl for a month. I was afraid that it would mess with his natural immune abilities, and I think I was right. He developed a small bald patch about 2 weeks ago on his back right leg. I took him to the vet today and they said he had a genetic form of demodectic mange where it will progress to total hair loss and possibly death if I didnt treat it with weekly 'dips'. The problem is is that he is so young, and only 6 pounds, and I am not sure how much more his poor body can take. The 'dips' are also very costly, they plan on doing 8-12 dips at $40 a dip. I have begun using the Goodwinol ointment today, and I am supposed to rub it on twice a day. Am I treating him right? The vet says no, I am not being aggressive enough. What should I do?