1)
Why does it say "Im Esak Shamayim Sham Atah"?
1.
Radak: If I would think that I can ascend to Shamayim and not find You, You are there.
2.
Malbim: [If I would ascend to Shamayim], You are there, for it is the dwelling of Your honor.
2)
What is the meaning of "v'Atzi'ah"?
1.
Rashi: I will set a mat to lie on.
2.
Radak #1: It is to descend, just like Matza (a mattress) is under a person.
3.
Radak #2: This refers to the grave, which is man's bed in death.
3)
Why does it say "She'ol Hinecha"?
1.
Malbim: Even though Your dwelling is not below, Your kingship rules everywhere.