The 70 who went down to Egypt

When a person tells a lie, the initial lie is not that hard, what gets a person into trouble is all the subsequent the lies that they need to tell to keep their story consistent. A good example of something similar is in parshas Vayigash.  The Torah details the descendants of Yaakov who went to Egypt and says that there were 70. However, this raises a few problems with explanations that Chazal gave earlier and leads to Chazal/Rashi having to give more and more difficult answers to keep the story consistent.

I. The twin wives of the Shevatim

In this post Who did the שבטים marry?, I quoted Rashi who was bothered by the question, who did the Shevatim marry and he quoted one opinion in Chazal that Each שבט was born with a twin sister whom they married. In Vayigash, Rashi now has to deal with the ramifications of this explanation. Rashi is bothered by the question, how come these twins aren't listed as going down to Egypt. Rashi is forced to answer that they must have died. But, this raises more questions then it solves:

1. They all died while all their brothers lived?
2. The Torah explicitly states that the list of people going to Egypt did not include the Shevatim's wives. ל־הַ֠נֶּ֠פֶשׁ הַבָּאָ֨ה לְיַעֲקֹ֤ב מִצְרַ֙יְמָה֙ יֹצְאֵ֣י יְרֵכ֔וֹ מִלְּבַ֖ד נְשֵׁ֣י בְנֵי־יַעֲקֹ֑ב כׇּל־נֶ֖פֶשׁ שִׁשִּׁ֥ים וָשֵֽׁשׁ.
3. So who were these wives? If they were כנעניות then we are back to the question of how could they marry כנעניות which led Rashi to say that they married their twins.
4. The Torah says that there were 70 people and yet if you count it's only 69. Rashi quotes a Medrash that Yocheved was born as they reached Egypt. If Yocheved was born on the way then clearly Levi had a wife who gave birth to Yocheved, who was she if their wives died earlier?

II. Where are all the females?

1. The Torah lists 69 descendants of Yaakov. A grand total of 2 are females, Dina and Serach. In the real world, about 50% of babies are female, so does it make sense that the descendants of Yaakov were only 2.8% female?
2. Who did the descendants of Yaakov marry? Egyptian women? Who were the נשים צדקניות who chazal describe as saving the Jewish people? Egyptian women?