1)
What is "Madmenah"?
1.
Radak: We find this city among the cities of Mo'av, but not among cities of Yisrael. This is like I said (28), that a city can have two names. Perhaps it is the city of Yehudah "Tziklag Madmanah v' Sansanah" (Yehoshua 15:31); even though the Nekudos are different, the letters are the same.
2)
What is the meaning of "He'izu"?
1.
Rashi: They gathered to flee. Radak - this is like "Ha'ez Es Miknecha" (Shemos 9:19).
2.
Malbim: They gathered all their wealth to a place that will be safe from the enemy.