As sad as it will probably be for you, I would also have to
agree that re-homing the dog would be best. I do not like the
Idea of people just re-homing dogs because they dont fit in- but
in this instance, your poor dog is losing out on the freedom and
happiness that he has been used to. (A scared dog is not a happy
dog), and he could end up nipping or biting your son, if he was to
Invade the dogs space or get up too close to him whilst throwing
himself about.
I know you worry about the dog settling in with new owners, but
I think in the long run, it will be better for the dog to have a few
weeks of uncertainty (followed by a life of happiness), than keeping
him put, and having a life of sadness and restrictions.
I understand that you are you doing your best by putting the dog
out of harms way (in the kitchen), but as your son gets older and
bigger, he may start trying to pick the dog up or rough play with
him, and this would cause the dog to be even more guarded
and create bigger problems.
I do feel for you, as I would have the same problem giving up my
dog, and its obviously easier said than done - (but you cannot risk
your son being nipped/bitten in the future/or the dog being badly
hurt).
Hopefully a local (reputable) re-homing centre will be able to
find him his forever home.
As other poster said, its not your fault, or your sons, its just
very unfortunate it has come to this.
Good luck going forward.