1)
Why does it say "Zos Menuchasi Adei Ad"?
1.
Radak: He will not go from place to place like He did until now.
2.
Malbim: This begins the third part of this Mizmor - Hashem's answer [to the requests in verses 8-13. David said, rise to Your rest]; I do not rest here [like one who is weary] due to transience, and he will leave when he finds another resting place. I desired this place itself! (13)