1)
Why did he say "Hinei Hu b'Yedchem"?
1.
Malbim: I (Tzidkiyah) freed him (37:21), but since I have no power against you in anything, do to him as you want.
2)
What is the meaning of "[Ein ha'Melech] Yuchal [Eschem]"?
1.
Rashi, Targum Yonasan: [The king] cannot [answer anything to you].
2.
Radak: In Leshon ha'Kodesh, 'Ein' is not used with the past or future. We must say that it means 'the king is not worthy that he can do anything against you, against your will.
