I don't know if this will help you, and certainly there are more knowledgeable people on VJ than I, however, here is what I discovered. I had to renew my license the other day and asked about my fiance, so that we could be prepared when he comes. I was told by my DMV in Seattle that a) he can drive legally with his German license until he gets residency in Washington or

he could bring his German license, proof of identity (passport, birth cert) and his K1 stamp (or whatever the official name is) and a piece of mail showing his name and our Washington address. That's it. He doesn't need to surrender his German license nor does he have to take the driving or written test. I called another DMV to find out if this was true and was told yes.
Now, we are a high immigrant area, but I would assume that where you live is also? I think he unfortunately got a rude person taking out a bad day on him.

I forgot to mention that my SO already has a SSN and had a green card once before as a minor, so that may make a difference, but I doubt it. I didn't tell the clerk at the DMV this at any rate.
Hope this helps and if it doesn't, I know someone else will come along to help you