1)
Why does it say "u'Mes Aleihem"?
1.
Radak: He will die for (a) regretting his virtue, and (b) for doing fraud.
2.
Malbim: He will be punished for (a) abandoning his previous [good] path. The greater that he used to be, this increases the sin that he does now 1 . (b) For the sins that he does from now and onwards. His sin kills him; I do not!