Sorry I didn't reply sooner, Shirley, I've been away from the computer for a few days. With my limited expertise, I don't know how much I can help you, but I'll give you a couple of thoughts.
First, you say in your post that you found the 78th was not deployed to Europe until 1945. That is incorrect, I believe. Stanton shows the 78th ID arriving France 22 Nov 44, and the 311th Infantry entering combat the first week in Dec 44.
AR 615-365, Convenience of the Govt, RR 1-1, (Demobilization) is seen on many discharges. AR is Army Regulation. It simply means the war had ended, the Army was gearing down, and they no longer needed the large number of personnel, so they were discharged.
I can't get anything out of "Company 3217 Sig. Jerv.BIV" My guess would be this is a typo, or you have misread it. Could it be 3217 Sig Serv BN? That would be 3217th Signal Service Battalion. Perhaps he ended up in one of the companies in this outfit following recovery from his wounds received near Brest. (Though it would seem odd to me that they would put a man with combat infantry experience in a signal corps outfit.)
As I said, I'm afraid I can't shed more light on it for you. Perhaps Dave can help further, he's much more knowledgeable than I am.