Oh no!
I am sorry to hear this!
I had a Shih-tzu that we rescured several years ago that had demodex mites/mange. He was older (2 years old). After several different meds, the vet then tried the dips (which I recall seemed pretty potent and were only given so often). He then tried Ivermectin or something like that (it seemed it was used as some sort of cattle medication, at the time)...it was pretty potent as well. The side effects were rough....I remember that our little guy started having eye problems being on it and the vet swore that was not a side effect to the drug, but at his next check up, I told him that he was having troubles seeing and the vet confirmed that he was pretty much blinded. The poor little guy was so sick, (from this and various other issues), he didn't make it long.
BUT his cause was unique because he had other factors that were NOT on his side. I have known of a few people that have had this issue to deal w/ and the outcomes were all postitive.
I know you will be able to find a lot of support and help on here. Good luck!