[Jeir]

There are a couple of pinned threads you can read through for advice. It seems you're doing all you can right now, although you may want to find some small pet-safe/baby-safe moisturising cream if Chowder starts to scratch and damage his skin (Sudocream was recommended in one of the pinned threads, if you can get that). You'll also want to add more bedding, as the fur loss and loss of condition will make him more susceptible to the cold.

Sadly, cushings isn't really something they can recover from, so you will have to keep an eye on his wellbeing and may need to take him to the vet for his final rest should his quality of life lower too much.