I was able to figure out both of my issues.
For the media files: I realized the textbook images for M&M 6e were not shared. I found an old Reddit post with an expired links, for which I was able to recover one of them using archive.org to download the majority of the remaining media files. I have uploaded it on Google Drive separately and can share that with others if anyone is interested in the as close to full media collection for the Ankithesia deck.
For the browser not closing issue: I don’t know why but the first 5-7 cards that were under the first ~15 empty cards were the problem cards. They were the only cards that cause the issue out of the 11K (yes I went through them all…). So I deleted those cards, which isn’t a lot in the long run, and now my Anki browser closes appropriately. Not sure what the issue was but it is also now fixed.