This thy son (ο υιος σου ουτος). Contempt and sarcasm. He does not say: "This my brother."

Came (ηλθεν). He does not even say, came back or came home.

Devoured (καταφαγων). We say, "eaten up," but the Greek has, "eaten down" (perfective use of κατα-). Suggested by the feasting going on.

With harlots (μετα πορνων). This may be true (verse Luke 15:13), but the elder son did not know it to be true. He may reflect what he would have done in like case.