You might be having an XY problem. Are you sure having a bunch of files with the date in the file name is the right thing to do in the first place, as opposed to something like using version control or a database?
Formatting of other stuff is outside the scope of the ISO 8601 standard, so do whatever works better for you.
Ok, so this is a pretty neat idea if you forget your documents by accident, but I wouldn't risk using it instead of physical copies.
Not sure if you can buy them but it looks relatively easy and simple to make using a raspberry pi or arduino microcontroller. Depending on where you can find a 7seg display and what length you want it to be, should be able to program it relatively quickly. Wiring shouldn't be too much of an issue either.
You can get 4 8-character 7seg displays for 12 dollars on Amazon. Should be more than enough to build a clock of your own.
When I set it to English (Sweden), week 2 is --01-11/--01-17, as according to ISO. Make sure it says Monday as the first day of the week. If it's set to Sunday, week 2 will be --01-10/--01-16 instead. You can change first day of the week in the app settings.
You can try to disable week numbering, force closing the app (open recents and swipe it away), and then open it and enable week numbering again. That might refresh it. You can also try restarting your device.
Are you using Google Calendar? Some people have made the mistake thinking the Samsung Calendar is the official in Android. The left side menu should say "Google Calendar" if you got the right one. If you aren't using the Google Calendar, the one you're using might be faulty.