In what sense will Hashem put His Torah inside them?
Malbim: They will fulfill My Torah amidst arousal of the intellect. It will be natural for them, like something inside them.
In what sense will Hashem write His Torah on their hearts?
Malbim: It will not need to be written on a Sefer with ink, for it will be written on their hearts. Its laws will be engraved in their hearts. The heart is the power of choice and authority in the Nefesh. There will not be aroused in them a choice contrary to Torah.
Why does it say first "I will be their G-d", and afterwards "they will be a nation to Me"?
Malbim: Clinging to Elokus will not depend on their deeds, via arousal from below, since choosing evil will not be feasible. The arousal will be from above via Chesed, and it will never depart in any circumstances.
