He clearly sounds overwhelmed with the changes in his life and you need to protect him too. Get a crate or two and, if you have company around, put him in his crate. He can then be with people without being overwhelmed. If he does not do well in a crate, either use a baby gate to place him in a different room (where he can still see people) or place him in another room by himself while the company is there.
He needs time to adjust and to settle in before you expect him to be good with unpredictable people.
Sabra - female GSD - born April 30, 2012
Sargeant - rescued senior GSD male/foster failure - approximately ten years old (August 2013)
Max - rescued GSD - Dec 22, 2010 to March 7, 2012 - at the bridge
Sable - rescued GSD - at the bridge