Hi
so glad Bracken was saved it is hard sometimes for vets to diagnose in time.
Our dog Amber had it for 10 years she was not pure GSD but had a lot in her. She got it before she was 2 years old and just collapsed as you mention a 'crisis'. IT took us a year of visiting the vet to get her stable! over the years we had to increase the florinef to 18 tablets a day and other tablets but she had a good life albeit not a normal one as we had to be careful not to stress her. even a trip to the vets can be fatal if they are 'low'.
If you need to know anything please ask, we have had 10 years of caring for her and have learned a great deal. she was very happy and died June 2009 when her back legs gave way and we decided that she was no longer happy then.
There is no reason to think your absolutely beautiful dog won't live a good life, I have never seen colourings like that!
I am sure you know to reduce stress as much as poss and we have had many crisis during the years, the earlier you recognise them the better. Amber also began on a drip thankfully not in such a bad condition as poor Bracken. Aren't they brave
Just to let you know we put a pinch of salt in her meal every day and that helped her electrolytes although it is not a veterinary fact but sort of an experiment one of our vets colleagues suggested. We definitely noticed a decline when we did not give salt.
wish u all the best, at least you know now
Sarahx