Why did Yosef consider it important for Pharaoh to know that his brothers were shepherds?
Seforno: In order that he allow them to settle in Goshen. 1
Why did Yosef find it necessary to tell Pharaoh that his brothers were shepherds before they themselves did?
Seforno: So that, when the brothers told him, he would believe them - and not think that they only said so in order to live in Goshen.
Why did Yosef say that he will ascend and tell Paro? (Before, he ascended to Goshen!)
Da'as Zekenim, Hadar Zekenim (29), Moshav Zekenim #1: He had descended from his chariot to speak to his father. He asked permission to ascend on his chariot [and tell Paro].
Moshav Zekenim #2: It will be an ascent for me. Initially, people disgraced me and said "see a slave ruling!" Now they will see that I am not a slave, rather, I come from great ancestors, and they will praise me.
רש"י: ועוד אומר לו וכו': למה פירש רש"י כך?
גור אריה: קשה למה כפל רש"י ואגידה...ואומרה"? אלא- אגיד לפרעה שאחי באו, ואומר לו שהם רועי צאן.
רש"י: ועוד אומר לו: למה לא כלל יוסף את הכל בדיבור אחד?
גור אריה: מידת דרך ארץ שלא לבא אל המלך ולבקש מאתו שישבו בארץ גושן אלא רק אגב שהוא מספר על בואם.