I had the same experience with a Greyhound. He was a blood donor for 2 years at the emergency vet my daughter works for and he needed a home, so we brought him home and he was terrified! We also have a busy household and this poor dog didn't know how to act.
It was hard but we had to give him back and he was adopted by a lady at the vets who has a less hectic household.
Sometimes what's best for the dog isn't what's best for our hearts!
You did great! From beginning to end you looked out for the lil guy!