Either is OK. Ending is more specific and is used to describe the end of a story. You would say "end of the road" but never "ending of the road." But either is one is OK for books, movies, etc

The appropriate word used is "climax" of the film. if u want any one from ending /end i would say as end rather than ending

The ending of the film would be the last part. The end of the film would be when you get up and leave.