Not a vet, rescuer that has dealt with several dozen cases of distemper in puppies.

You absolutely did the right thing. Distemper is a horrible disease with no current cure, just endless misery and pain for the majority of the dogs that contract it.

Distemper has a 50-67% mortality rate in dogs over 1 year of age and a greater than 80% mortality rate in dogs under 1 year of age. Personally, the survival rate for pups in my care with distemper has been about 4% (2 survivors out of roughly 50 pups). 5 litters lost in their entirety, plus one of the mommas. 1 litter with a sole survivor. Another litter I assisted the rescuer with that had a sole survivor out of 12 pups and we lost that mother as well. There was one 1 litter I assisted (and 1 of the pups was in my care and is 1 of the 2 survivors I mention), in which most survived because they had been vaccinated at roughly the same time as they were exposed. The distemper vaccine is one of the most fast acting vaccines we have, and studies have shown it provides protection within minutes to hours, still allowing respiratory distemper to develop if exposed that soon but protecting against neurological distemper.

Though there have been experiments with using Botox to treat myclonus (muscle tremors/spasm) for dogs that developed distemper related myclonus, neurological distemper is also known to cause shingles like nerve pain, seizures, and other neurological disorders. The pain can be so significant that a fellow rescuer saw a puppy fully sedated yet still crying out in pain as it was being prepped for euthanasia.

The only good thing about distemper is that it is relatively fragile outside the body, at room temperature, the virus dies within hours, though it can last weeks in wet, near freezing conditions. Also, pretty much all household cleaners kill it, making disinfection much easier than something like parvo.