I know the pain that you are feeling. I went through that twice. When I had to put Rosco to sleep for his agressiveness, and when I rehomed Teddy because I couldn't handle him. It is such a difficult decision.
I really think that you should give Oz more time. Those type of dogs are soooo hyper and take so long to mature, but they do. Dusty was really wound up forever. There were times where I didn't even enjoy being around him because he was so high maintenance. I am happy to say that at 3 years old, Dusty finally mellowed out. He's a great dog now. I honestly thought he'd never calm down though.
I know that you love Oz and you will make the best decision for him. I stand behind you no matter what you do.