1)
How should Hashem hide His face from his sins?
1.
Radak: They should not be in front of Your face to remember them and punish further for them.
2)
Does David ask to erase also future sins?
1.
Radak: No - only those until today.
3)
Does he ask to erase only Avonos, but not Chata'im?
1.
Malbim: Yes. Chata'im are in action. They are external to the Nefesh, just like one who makes something is separate from what he made. David asks that Hashem not look at them. Avonos are in thought. They are on the Nefesh, like words written on a paper or etched into a tablet. He asks to erase them from his Nefesh.
