What fear does the verse command about?
Malbim: It is awe of Hashem's exaltedness, and not fear of punishment.
What is "b'Samim uve'Emes "?
Radak: B'Samim is a noun [in purity or simplicity], and not an adverb (purely or simply). The same applies to "be'Emes uv'Samim" (Shoftim 9:16).
Malbim: A fake Avodah is not Emes. Avodah in order to receive reward is not b'Samim.
What gods does he discuss?
Radak: It is what they took from the cities that they captured.
Malbim: He refers to serving Hashem and something else (Shituf). .
Where do we find that they served idolatry in Egypt?
Radak: Yechezkel 20:9 ("Gilulei Mitzrayim Lo Azavu").
Why does the verse command twice to serve Hashem?
Malbim: The latter commands to serve Hashem alone, and not Shituf (Hashem and something else).