Bless you for adopting your special little one.
My Yorkies have always been rescues as well, and they are quite different than Yorkies you get from reputable breeders.
Because you don't know their history - if they've been abused, what they've witnessed, what they've had to face on a daily basis - it can sometimes take a long time for them to understand what having a loving home is all about. Even the small things like coming across the threshold of a door can be scary for them.
Both my rescue girls love sleeping. They had never done anything but sleep, they were used for breeding only, kept in wire cages and never felt the loving hand of a person. So for them, sleeping a lot was something they have always done.
Neither of our girls ever learned to jump up and down off of furniture - they've never been on a sofa or in a bed, so jumping up and down from anything is something they never do. Our Chihuahuas on the other hand, LOVE jumping around like Mexican jumping beans. LOL! Our rescue girls also have difficult determining perception, what's dangerous, etc. They also do not like using grass - they prefer our driveway or sidewalk.
Our rescue babies also can't walk up and down stairs. Rescues are precious babies but they have been faced with so much and sometimes they never act like a little one raised in a loving home from a pup.
As for his skin, I always like to work from the inside out - so making sure our girls had the best food was first for us. No wheat, soy, gluten, grain, artifical colors/preservatives, etc. if you want to be on the safe side. There is also natural remedies that have worked wonders for us. First is fish oil - you can give it in a dropper or put some on their food. I got a large bottle from our vet and give it to all our babies. Makes their fur extra soft and soothes their skin. Also good for the heart.
I've also used a liquid called "Skin Aid" (Moist Dermatitis)- you can purchase this from most family pharmacies or natural herb stores. You can give up to 15 drops in their water or 4 drops by mouth daily. This really helped our Yorkie who had very serious dry flaky skin - she continuously itched and scratched herself and would chew her feet. A few days of the skin aid and it really helped her heal up.
As with anything I guess consistency is key in getting our rescue babies up to par health-wise. And its always great doing a complete checkup, bloodwork, etc. at your vet just to find out if there are any underlying health issues - just another thing that can be questionable with a rescue since we don't know their entire history.
Rescues take lots of work, love, patience but they love so much more in return.
Sorry for the long post! I didn't realize how long it was until I was finished.
I am so glad your new boy has a wonderful caring home, bless you for opening your heart and home to him. Thank you! I know your new boy will have the best love and care possible.