Глава means head. Would an acceptable translation be head director or chief director?
Unfortunately, Duo still doesn't accept either "head director" or "chief director" as of 11 Oct. 2017.
Yes, only for a movie director.
Edit: also for a theatre director, as vmar33 pointed out.
The word “директор” is not used for film directors (they are “режиссёры”). “Директор” is either a school principal/headteacher or a head of a company or some office.
Is this contrived or is this term used in Russian? In English, the "main director" is simply "director" and the other directors are qualified - e.g. "assistant director".