How to make a Pomeranian coat healthy?

Since I was a child I always wanted on of these large breed dogs and I recently rescued a toy pomeranian. He weighs about 4 pounds and is around 6 years old. He is so adorable. His coat is kinda rough. Is that normal. It also looks a bit thinned out. Is there anything I could do to make his coat healthier? Maybe feed him something. I don't know, any advice will help. Thanks.
I also want to add one more thing. He is not nuetered. Do you think he is to old to get nuerterd now? Will it change him for the bad or will it be ok?