You do not need to be short in your postings!
Your post is very easy to read and explains a lot. I just wish I had some experience that I could share with you, but I don't. I do know that a few people here have had experience ... lots are not online on weekends, so it may not be until tomorrow before you see more replies. You could do a search using the search option...type in Cushings and I am sure you will find a lot of helpful information on YT.
The Melatonin dosage is just what my foster pup is on. I am SO sorry.....BID is twice/day. I normally don't write it that way...I do apologize.
I am glad your husband set your vet straight! Sometimes people say things like that without thinking....very nice of him to call you and explain everything in detail!
Yes, Cushings can take a long time to diagnose...that I do know. It is a bit hard to understand as well....but it sounds like you are going to get the hang of it and hopefully your pupster will do well.