Just wanted to update that my husband received COPR yesterday morning.
Though I said he received "PPR" on Tuesday, as a German (i.e. visa-exempt) citizen he didn't actually have to submit his passport at all. No scans or additional photos were requested either, even though his photos were from last August. The message he got from Vienna on Tuesday was actually them confirming they had documents ready to send him and asking him how he wanted them delivered (the letter is somewhat confusingly written, as it refers to his passport being ready to be returned, but I figured they just meant COPR).
As others have mentioned in the past, Vienna gives you the option to have it couriered if you make all the arrangements yourself or you can have them send it for free by registered mail. We opted for the latter, since registered mail from Austria to Germany should be very reliable. I believe it was sent Wednesday, so it only took two business days to arrive.
I'm somewhat amazed that everything is actually settled, and very, very grateful that everything went so smoothly in the end. I'm especially relieved that this means we don't have to worry about applying for a student permit for my husband at the last minute and can just land immediately and get on with things.
Thank you to everyone for your advice and company on this crazy-making journey. I feel very lucky to have had such a smooth ride, and I hope that everyone who is still waiting experiences the same from here out! If I can be of any help still, don't hesitate to let me know. Until then, fingers crossed for you all!