1)
What is "Lev Sorer u'Moreh"?
1.
Malbim: Lev is the power that arouses all natures and Midos in the Nefesh; it is the source of all bodily desires. Also [the Am 1 ] has a heart that wants to rebel against the Chok Klali. They should have submitted to the Chok, like the sea does - but they did not.
1
I.e. just like the sea desires to pass its border. (PF)
2)
What is the meaning of "Saru"?
1.
Radak: They departed from the good path, and went in the freedom of their hearts.
2.
Radak citing Targum Yonasan: They veered from My Avodah.
3.
Malbim: They transgressed the Chok Klali (fear of Hashem Himself).