Well, I do know only a little about it bc my Wylie has the opposite of Addisons, which is Cushings - and Wy actually has Atypical Cushing's disease. I give Wy a chemo pill 3x week - the goal is to "shave away" layers of his adrenal glands - BUT if we go too far or the med is too much, you can actually then CAUSE Addisons. Cushing's is extremely complicated.
If your kiddo has Addisons - you'll probably have to medicate w/ a cortisone type drug for life, but at least the treatment is pretty straightforward - and this is good.
I hope your baby gets a firm Dx soon. Here is more info:
Addison's Disease (Hypoadrenocorticism) in Dogs