1)
Which men did he address?
1.
Malbim: Those who know that their wives offer to Meleches ha'Shamayim.
2)
Since it says "Kol ha'Am", why does it detail men and women?
1.
Malbim: All who dwelled in Pasros offered (verse 15). Of those elsewhere, only those who offered, or knew that their wives offered, answered Yirmeyah.
3)
Did he speak to them in the name of Hashem?
1.
Malbim: No. This he answered by himself. Verse 24 begins what Hashem told him to reply.