I think that my Doobie is a very good representative of the breed and so did many judges so we can look at his picture and describe a good breeding dog.
Doobie finishing picture.jpg
Okay Doobie has small ears that are set high on the top of his head.
He has a very cute little face with beautiful shades of gold
His body coat is a dark steel blue
His top line is very straight , no roach in it
He is balanced in his leg height as to the length of his body. compact
His tail set is high at the end of his back
These things you can tell from a picture, but there are even more important things to check , like soundness and movement.
The things your dog has are very important also like his great disposition, but for a breeding male he needs a lot of things in one package.
As far as you wanting to find a 4 pound female to breed , well most responsible breeders will not breed anything under 5 pounds for a female and then it is always a risk.
YT is a very good place to learn, your boy looks very sweet.