1)
Did David assume that the angel will not strike David?
1.
Malbim (Shmuel II, 24:17): Yes, for the angel saw him, and tilted his sword towards the people.
2)
Why did David call Yisrael "ha'Tzon"?
1.
'Rashi': They are like flock animals being brought to Shechitah. They cannot evade it, for they are destined for Shechitah!
