Why did she tell him to curse Hashem?
Chidushei Ge'onim in Ein Yakov Bava Basra 15b, citing Ein Eliyahu: One opinion (in Bava Basra 15b) holds that she was Dinah. Surely that Tzadekes did not tell him to curse Hashem! Rather, she held like the opinion (in Shach YD 157:1) that a Kadosh may kill himself amidst concern lest he succumb to sin. You cannot continue to bear the afflictions; perhaps you will get angry at Hashem! Bless Him for what He gave to you, and kill yourself! He rebuked her for assuming that the afflictions will persist 1 .
Malbim: The first time, he blessed Hashem. Now, he was silent; his heart was not complete now. To anger him, she said humorously, the first time, you blessed Hashem and He increased to afflict also your body. If you will bless Him now, He will need to strike you more until you die! Since you persist in your purity, why do you not bless Him?
Four verses after this, Iyov cursed his day! That was much later, after his friends came; they lived 300 Parsa'os away from each other (Bava Basra 16b), so it was a journey of at least 17 days, even if Iyov was in the middle. He rebuked her when he was bodily afflicted; he thought that it will pass soon. (PF)
What is the tense of "va'Mus"?
Rashi: It is a command, like "u'Mus ba'Har."
