This is a great question. You’ve also provided an excellent example others can learn from.
Ordinarily, the adjusted margin begins with line 1 and ends at the final line number. Any intervening text—numbered or not—must follow the adjusted margin. Outside the body of line-numbered text, the full line width is used.
Stage directions and scene settings must follow the adjusted margin when they occur between line 1 and the final line number.
However, I like your use of the adjusted margin with the initial and final stage directions. The use of blank lines sets the dialogue apart from the surrounding text. It makes sense to use the adjusted margin. The guidelines are not clear in this situation.
But the example you provided has the unique quality of restarting the numbering at each scene. Each scene has notes that reference the line numbers. This structure may present unique challenges for the reader.
My suggestion is to use the full width of the page for scene numbers (centered headings) and scene settings that precede each instance of line number 1. Restart the adjusted margin at line 1 each time. This will help the student find the scene-specific line numbers when following classroom discussions, locating reference notes, and answering questions in exercise sections. Imagine a child called upon to find line 10 of the third scene. With the teacher and students waiting, the nervous child is scanning quickly for the number. A change in margin signals that numbering resets with each scene.