I can honestly say I feel your pain because I have been there.
I adopted a dog for my son as a Christmas present from a shelter adoption agency in NJ. I drove 4 hours to get this dog because there were no Puppies around here except in the puppy mill stores in the mall and I couldn't afford them.
The one we adopted got glowing reviews from the agency so I took her home.
I took her to the vet AFTER the holidays and the vet noticed some behavior abnormalities and told me I should get rid of her quickly, don't let the kids get too attached. Too late, we were attached the first day.
She would be great for days, then would go crazy and destroy anything and everything, once she bite right through the support of my kitchen chair in one bite. She bite my sons and broke skin a few times but once I saw her bite through the wood on the chair that was about 1" in diameter I knew the harm she could do if she ever bite like that into skin.
We took her the next day to the Vet to have her put down. They told me they could possibly find someone to adopt her but if I did that I would have to foster her until they found someone and I couldn't have the dog in the house while we waited, especially if no one was ever found. I also didn't want my boys becoming more attached.
They were upset for a while but we waited till the spring and found the most fantastic dog at the city pound. He was 3-5 when we got him and we had him for 17 years until we finally ahd to put him down because of his health.
We just drove home from FL and while were were down there we stopped at PetCo to buy a turtle and came home with a black lab/retriever mix puppy who is now the love of our lives.