1)
Why does it say "Lo Echpotz b'Mos ha'Mes?. [v'Hashivu vi'Chyu]"?
1.
Radak: Even when alive, he is called Mes, based on his end. This is like Targum Yonasan 'd'Chayav Limemas' and Targum Onkelos of "Yumas ha'Mes" Devarim 17:6 - 'd'Chayav Ketol.'
2.
Malbim: I will accept even Teshuvah amidst fear, for I do not want him to die. Also, via this, later he will come to Teshuvah amidst love, and his earlier sins will become merits, and he will live eternally 1 .
1
Even without Teshuvah amidst love, he would live eternally based on his future Mitzvos! Hashem desires that he have better eternal life via the previous sins. (PF)