What is the authenticity of attributing to Adam his saying to Eve: "Get away from me, for I came from you, so leave me to the angels of my Lord"?

The meaning of "Away from me!" is: move away from me and keep your distance, and its repetition is for emphasis.

The intent behind Adam's statement to Eve, "Leave me and the angels of my Lord," was that Eve should not come between Adam and the angels who had come to take his soul, because Eve tried to seek refuge with Adam when she saw and recognized the angels.

As for his statement, "Indeed, I was afflicted because of you," it is likely a reference to Eve's incitement of Adam to eat from the tree.