[Milhouse]

C:\Python34\python.exe C:\texturecache.py watched movies backup movies.dat (copy and paste into CMD)

Yes, that should work (see previous post about running/installing in Windows if you have a problem).

Substitute "tvshows" for "movies" if you also want to backup your tvshows, ie.:

Code:

C:\Python34\python.exe C:\texturecache.py watched tvshows backup tvshows.dat

Then I will remove the sources, delete all the nfo's, re-add the sources and scan them in.

At this point, do I need to export this library so that nfo's are created again?

You don't need to, but you can export them again if you want to.

And to retain the watched status:
C:\Python34\python.exe C:\texturecache.py watched movies restore movies.dat (copy and paste into CMD)

Yep.

1 last thing. Can 'Date Added' be retained also?

"Date Added" is the file modification date of the movie (and not the date it is added into your library) so this shouldn't change after you're reloaded the library.