1)
What is the meaning of "Havah Lanu Ezras mi'Tzar"?
1.
Radak (60:13): Just like You helped us until here, so help us from every affliction that will occur. There is a Sov at the end of Ezras, even though it is not Samuch. There are many cases like this, e.g. "Avi v'Zimras Kah" (Shemos 15:2).
2)
Why did he say "v'Shav Teshu'as Adam"?
1.
Radak (60:13): The only salvation is Yours, for man's salvation is vain.
