What is "Mesom"?
Radak: The root is Tamam - perfection, health. Rather, my entire body is plagued. Malbim - this corresponds to "va'Tinchas Alai Yadecha" (verse 3).
Radak citing his father: The root is Mesah. This is like "Mesei Mishpar" (Bereishis 34:30). From my many plagues, human form does not remain in me.
Why did he say "Ein Shalom ba'Atzamai"?
Radak: Even my bones, which are strong, have no peace; they ache.
Malbim: My 'bones' (inside) has no peace; they are full of sighing and despair due to the sin. This corresponds to "Chitzecha Nichasu Vi" (verse 3).
Why did he say "Mipnei Chatasi"?
Radak: Your anger is not for naught. One must justify Hashem's judgment, whether or not he knows the sin [for which he is punished].
