I'll try to help, Shirley, and if someone with more knowledge can weigh in, so much the better.
To quote Dave B, "You can't necessarally associate what is on the discharge with the unit he SERVED with. It was very often the case that a man served his combat time with one outfit, and then at the conclusion of hostilities or due to requirements elsewhere, he was transfered into another unit to either be demobilized or reassigned. This happened a lot!"
HQ, 2nd Bn, Glider Infantry doesn't tell us much, because it doesn't tell us WHICH glider infantry. All glider infantry regiments would have had a 2nd Battalion, I believe. However, based on what he told you, and the info you gave us in your first post, I don't think it makes much difference. (See DB's quote above.)
Now, what to make of the 175th Infantry and 311th Infantry?
You said he was hit on Omaha Beach, and again later, near Brest. The 78th ID didn't get to France until 22 Nov 1944, over five months after Normandy D-Day, and a considerable time after any significant action around Brest, I believe.
The 175th, on the other hand, got assault credit for Normandy. In addition, Stanton's combat narrative for the 29th ID says, in part, "The division was moved west by motor into Brittany to positions outside the fortress of Brest, which it began attacking 25 Aug 44." This suggests to me that, up to his wounding at Brest, he was in the 175th Infantry.
I have a suspicion that, following his recovery, he may have been re-assigned to the 311th Infantry. My reason for this suspicion is that in your original post you noted his battles and campaigns as, Normandy, Northern France, Rhineland, Ardennes. The 175th did not get credit for Ardenne-Alsace. The 311th, however, did. Oddly enough, both received campaign credit for Central Europe. Was the reason that he did not receive such on his discharge the fact that he went home before that campaign began? That would be one explanation. Another would be clerical error, which in WWII service info are LEGION.
Other than Stanton, etc, this is all supposition on my part, Shirley, but it gives you some ideas with which to work.