What did Lemech mean when he said to his wives, "Ki Ish Haragti l'Fitz'i, v'Yeled l'Chaburasi"?
Rashi #1 and Targum Onkelos: After Lemech accidentally killed Kayin 1 (his great-great ... grandfather), and his own son Tuval Kayin, 2 his wives did not want to be intimate with him. 3 To appease them, he declared, 'Did I kill a man by striking him deliberately, or a boy by deliberately wounding him'?
Rashi #2 (in 4:24) and Targum Yonasan: Having born him three sons (and a daughter), his wives, knowing about the forthcoming Flood, separated from him. He replied, "Did I kill a man and a boy (i.e., Hevel, who was a man in stature, but a boy in years)? And if Kayin, who did, was granted a reprieve lasting seven generations, how much so will I, who did not!'
Seforno: 'For (when) I killed a man (Kayin) I wounded myself, since the dead man was my (grand)father; and (when) I killed a boy (Tuval Kayin) I bruised myself, since the dead boy was my son'. 4
Ramban #1: Refer to 4:24:1:3 .
Ramban #2: Lemech, a highly intelligent man, taught his children all the Chochmos mentioned above (in 4:20-22), including implements of war. Consequently, his wives were worried that he would be punished for plying his ancestor Kayin's trade (that of murder). He therefore tried to assure them that, unlike Kayin, he had not murdered 'a man of his wounds or a boy of his bruises' (swords and spears are not synonymous with death, as there are ways of killing that are more painful than with a sword).
Oznayim la'Torah: Refer to 4:23:1:1 . He was pleading with them to be intimate with him because he had just killed two people - Kayin and Tuval Kayin - not because they were his flesh and blood, but because he had diminished the world's scant population by two. 5
Da'as Zekenim (to 4:15): "L'Chaburasi" means 'it will cause my death', due to Hashem's promise to avenge whoever will kill Kayin.
Rashi: Lemech, who was blind, was once hunting, and Tuval Kayin, his grandson, would help pull the bowstring (and aim the bow). Tuval Kayin saw what he thought was a Chayah (Refer to 4:15:3:4), but after they shot at it and killed it they discovered that it was their great-great ... grandfather Kayin. In his grief, Lemech clapped his hands together and inadvertently killed Tuval Kayin.
Because he had killed Tzilah's son and great-great-grandfather.
Refer to answer #1.
Why did Lemech want to be intimate with his two wives immediately after killing Kayin and Tuval Kayin?
Oznayim la'Torah:. Precisely because he had just killed two people (refer to 4:23:1:1) - bearing in mind that the world population was still sparse - he now wanted to bring two more babies into the world to replace them.
Why did Lemech address his wives as "N'shei Lemech" and not 'Nashai'?
Rashi (in Vayeira): Refer to 19:24:2.1:1: check online