1)
Why did he say both "Ha'azinah" and "v'Al Tis'alam"?
1.
Radak: The matter is repeated in different words.
2.
Malbim: Hearken to my Tefilah, i.e. pouring my Nefesh to Elokim (to save me from Avshalom), and do not hide from my Techinah, i.e. request for my other needs.