I am so sorry to hear about your little furbaby. Keep loving on him & see if you can find some toys he likes to play with. I would spend as much time on the floor with him as possible.
As for his coat. I use The Missing Link - I take Bubba & Roxie to a holistic, acupuncture vet and buy this food supplement there. But you may be able to buy it from pet stores.
Bubba was having some skin flaking problems, but I started adding this to their very high-grade human quality pet food (Flint River Ranch) and I saw a major improvement in the coat & skin of both dogs.
I just googled "The Missing Link pet" and tons of links came up - testimonials, links to buy, info on the product. Give that a try
Best wishes for the adjustment phase
yorkiesmiles
