1)
Regarding Osni'el, it said (verse 9) "Moshi'a... va'Yoshi'em." Why does it say about Ehud only Moshi'a?
1.
Malbim: Osni'el also judged Yisrael in Torah matters. Ehud merely saved them from their afflicter.
2)
What is the meaning of "Itar Yad Yemino"?
1.
Rashi citing Targum Yonasan: His right hand was shriveled; he could not use it skillfully.
2.
Rashi: In Hebrew, Itar refers to closure, like "v'Al Tetar Alai Be'er Piha" (Tehilim 69:16). He could not use it skillfully. (He was left handed - Radak.)