I am so sorry to hear about your Henry. I can tell you that for the past 2 months I have been dealing with Addison's in my Kuma. There is an Addison's board and those there are very knowledgeable about the disease and I've learned a lot since joining there. I knew nothing about Addison's when my Kuma got sick. He was, in the beginning, treated for renal failure, as he had a lot of the same symptoms, and the treatments didn't help. So, with that information and a vet that had experience with the disease, she did the 2 hour test and found that Kuma did have Addisons. He was a pretty sick little boy. Once the disease was diagnosed and Kuma was put on the shot (every 25 days or so) and a very small dose of Prednisone. It takes some adjustment to get them on the smallest dose of Prednisone possible and still keep them well but it is so much easier than not knowing what is wrong and not knowing what to do next. I am so new to this yet if I can be of any help don't hesitate to drop me a line. You are definitely on the right track if Henry does have Addison's. Keep your chin up!
The Addison's list can be found at:
http://pets.groups.yahoo.com/group/AddisonDogs_/