1)
Who are "Shorerai"?
1.
Radak: They are both from Yisrael, and from Goyim that I am exiled among them.
2)
Why does it say "Marom"?
1.
Rashi: This is Hashem, who dwells above. Radak - he calls to Hashem, who sees that many fight him.
2.
Malbim: [My enemies] say that many fight against me from above; Hashem agrees to kill me, and from above they fight me. This is Sheker! Only Enosh (a man) wants to swallow me, but not from above!