Here is a pair of sentences from A Midsummer Night's Dream that anyone who has ever spent a sleepless night can relate to:
"O weary night, O long and tedious night,
Abate thy hours....
And sleep, that sometimes shuts up sorrow's eye,
Steal me awhile from mine own company."
For diagramming imperative sentences, I think it is a mistake to put an understood "you" in parentheses. Parentheses are already being used for appositives.
An "x" will suffice for the understood "you".
LF
"(You)" is commonly used by online Reed-Kellogg teachers for imperative sentences. They say, "The 'you' is understood". It's evidence to me that they are not going to go the whole way with the art -- which ultimately has to deal with the enormous amount of ellipsis in speech.
I agree with your diagram, except that I think there was another "o" in it.
LF
I just float interjections, nouns of direct address, and absolute phrases anywhere up above the clause they are most closely related to.
Yes,
"Vocatives" I know because I have studied Latin. Here across the Atlantic we call them "nouns of direct address"
LF