Why does the Torah not insert the word "Im ", as if it is referring to a fait accompli?
Ramban: The Torah deliberately omits "Im", because it serves a dual purpose as a warning and a prediction - to predict that they will sin and that the punishment that follows, like the sin, is preconceived.
Why does the Torah insert the words "ve'Noshantem ba'Aretz"?
Ramban: Because once they have been a long time in the land and feel secure, the likelihood exists that they will forget Hashem and start turning to other gods.
Ramban: This hints at the first Galus (Galus Bavel).
Rashi (in Yechezkel, 7:2): Four hundred and forty years until they built the Beis-Hamikdash and four hundred and ten years until it was destroyed. In fact, they went out after eight hundred and fifty years - two years earlier, in order to prevent the fulfillment of "Ki Avod Toveidun" (in the next Pasuk), as intimated in Daniel. 9:14 - that Hashem performed with us an act of Tzedakah in taking us out before the designated time.
Why does the Pasuk not add "Va'avadtem oso"?
Ramban: Because it is talking about making an image and not about serving idols. 1
Why does it add "Va'asisem ha'Ra"?
Ibn Ezra: To other Mitzvos that they would contravene - such as murder and adultery.
And what are the connotations of "Lehach'iso"?
Seforno: They sinned in order to remove the Shechinah from Yisrael, so as not to be subservient to the Torah of Hashem and to His Mitzvos.
It also implies that they would sin Lehach'is (to anger Hashem), and not le'Te'avon (for pleasure).