1)
Why does he ask "Mah Tishtochachi Nafshi"? This Mizmor did not say Nafshi Tishtochach!
1.
Radak: The previous Mizmor said so; both of them are the same matter.
2)
When will His salvation come?
1.
Malbim: It is at a time of Ratzon (when He desires); it depends on Him, so hope to Him. Surely He will fulfill His promise!