Rashi: It is bowing, like "Shachah le'Afar Nafsheinu (44:26). When Shach is in the Hispa'el form, a Tov separates the letters of the root, like any word that the first letter of its root is Shin.

Malbim: He answers his Nefesh - I heard that (a) you feel lowly, for you despair that the light distanced from you, and (b) you are astounded that I do not pass over thorns to Beis Elokim. Both of these are not justified. Do not be astounded at me; wait for Elokim. Salvation depends on Him, when He will want! Also, do not feel lowly and despair, just wait for Elokim, like one who waits for something promised. The time will come to when I will thank Him for Yeshu'os Panav, when He returns His Shechinah to you!

Rashi: Wait and look forward to the Ge'ulah.

Radak: This is consolation after recalling the prior Simchah. Hashem will save me and take me out of Galus, and I will do like I used to!

Radak: This is like "u'Mal'ach Panav Hoshi'em" (Yeshayah 63:9). Radak there - He arranges causes to save them. The causes come out in front of Him; they are not chance.

Rashi (3): This is a Nevu'ah about the Churban. The three expressions allude to three kingdoms that will nullify Avodah in the Mikdash, and Yisrael scream and are redeemed - Bavel, Yavan and Edom.

Malbim (1): The first part of the Mizmor discusses return of the Shechinah. It is salvation of Panav - His face will illuminate on us, and not be hidden any more. The return of miracles afterwards are salvations of Panai vEi'lokai - through them are known His connection to Yisrael, and that He is their G-d - "Lo Me'astim v'Lo Ge'altim Lechalosam Ki Ani Hashem Elokeihem" (Vayikra 26:44).