Awwwww Big Bear is beautiful!!! I love shepards! I had 2 rotties, one was Bear the other his sister named K.C. They thought they were lap dogs....LOL Big babies!
You know, animals sometimes feed off our emotions just like kids do. And I think maybe split has a good idea about puppy training classes. That might be an option to look into. Do you crate your dogs? Maybe having a crate for puppy is a way for you both to get some much needed down time. Not to be used as punishment of course...but nap time, quiet time, bedtime type of thing. Also, pups don't like soiling their sleeping area, so if you were to crate and take out to pee etc....this may help in the training
What does your gut tell you about puppy? If it's really telling you this is not a good fit, then nothing will make it feel better. But, if it's telling you that you both have a chance, then you can go with that, no?
Wishing you and the puppy well. I know it's a hard decision.

sabby