1)
Why is it called "Bris Olam"?
1.
Malbim: Just like they will accept to serve Me always, the Bris I will make with them will not be conditional, rather, absolute.
2)
Why will Hashem put fear of Him in their hearts?
1.
Malbim: Since the Bris is unconditional, He must guard them from sin, which annuls the Bris.