Can I force Plex to use episode name from the file name this way?

The 3rd party “NFO Importer” agent will read all the info from the NFO file. I don’t know if it is still being maintained by the creator but the original thread is Here. Plex’s official agents will only read the IMDB ID.

Correct. Plex only reads the title tag from MP4 files. MKV’s use a different tagging system that Plex can’t read.