Thought I should post an update here. The "BIG problems with Jack" thread brings to mind a posting here.
About a week after I left messages, the Behaviorist called me back. They also do animal rescue, so they may have been pretty busy. Anyway - I spoke to Carolyn for about 20 minutes on the phone. She said she'd be happy to come over for a $95 visit, or I could take some instruction on the phone for free. Basically, she told me to do what Andrea initially advised. Put Duke on a thin, almost ribbon thin 10 foot lead with no hand loop. He is to have this lead on in the house at all times. That way when someone is coming or going from the house, the lead will be easy for us to step on and reel him in,so it's short enough for him to sit, and cannot lunge forward. We are to stay calm and quiet while asking Duke to "sit" or "down". She said with consistency, this will blow the wind out of his sails. But it will take quite some time because he has done the wrong behavior for a long time. We're still working on it. But, I think he's getting used to being stopped short with the comings and goings here.