Maybe he needs a home as an only dog. I fostered a young kelpie and found her a potential home. It didnt work out so I bought her home. She tried to get in the faces of my dogs big time and nipped me in her excitement (perceived as biting by the home who tried her out).
I soon got her sorted on the biting and my dogs sorted her on the issues of the in your face play. But she was perceived as in your face, bitey and difficult to control dog by people looking to adopt. But no way she could stay with me indefinitely, I have enough dog flesh on my hands already.
It seemed like it was going to be very hard to rehome her. Then we found a male triathlete who worked from home and had no other dogs. The kelpie was totally perfect for him and it worked out well. Best home ever for this girl.
Sometimes it just takes time but the prize is the perfect home for the dog.