Angels do not appear sitting, only standing!
Radak: Indeed, Yoshev means delaying 1 until Gid'on will turn to him. Gid'on did not turn to him, so he came to Gid'on. Also "Eshev Ad Shuvecha" (verse 18) and "Ashrei Yoshevei Veisecha" mean delaying.
Surely Acher explained like this. He had a tradition that angels do not sit (Divrei ha'Yamim 2 18:18 supports this), and he became a heretic when he saw Metatron sit [on one occasion] (Chagigah 15a)! (PF)
Why did the angel delay before appearing to Gid'on (verse 12)?
Radak: This teaches that Hashem is always available for Yisrael, if we will turn to Him and call to Him in truth.
Radak citing a Midrash: He waited until he found a merit for him, i.e. Kivud Av (refer to 6:11:6:1).
Why does it say "b'Afrah Asher l'Yo'ash"?
Radak, Malbim #2: There was another city Afrah in Binyamin (Yehoshua 18:23).
Malbim #1: The Elah (tree) was of Yo'ash.
Why is he called Avi ha'Ezri?
Rashi: He descends from Aviezer 1 ben Gil'ad ben Menasheh (Bamidbar 26:29-30).
There, he is called I'ezer. Usually Rashi points out when there is a change in the name! (PF)
Gas is where people make wine!
Rashi: He was using the beams of the winepress to beat 1 (Radak - i.e. thresh) the wheat.
Radak: He was beating the wheat in the winepress.
Radak: When people do so, it is called Chovet; when animals do so , it is called Dash. "Ki Sachbot Zeisecha" (Devarim 24:20) is hitting them to make them fall.
What is the meaning of "Lehanis Mipnei Midyan"?
Rashi: His father was beating wheat]. Gid'on honored him and told him, father, you are old. If the enemy will come, you cannot flee. Go, and I will beat!
Malbim: To bring the salvation, Gid'on needed merit and strength 1 , and Hashem would add to them. His readiness to flee shows strength.
What is his source? Barak defeated Sisera without a singular horse! Hashem later (7:4) told Gid'on that he has too many men!