1)
What is the grammatical form of "he'Me'anim"?
1.
Radak: It is an adjective. In the singular it is me'Ein with a Tzerei under the Aleph, therefore in the plural there is Chataf Patach under the Aleph.
2)
How will they be like the Ezor?
1.
Rashi: Their splendor (Radak - of Yehudah and Yerushalayim) will be like this corroded Ezor.
2.
Malbim: Just like it was put in water, and became dirty and improper to wear, so they refused to hear My words.
3)
What hints to going in the freedom of their hearts?
1.
Malbim: They sin b'Mezid, and not due to desire, just like Yirmeyah went intentionally to a far place to hide the Ezor.
