See http://mosaicmagazine.com/response/2015/03/how-to-judge-evidence-for-the-exodus/ If we say that elef means 1000 then how do we address these paragraphs in the article. If elef does not mean 1000 then how do we understand the detailed counts of the tribes in Sedra Bemidbar? For one thing, the book of Exodus (23:29-30) claims that the Israelites were so few in number as to be incapable of populating the land they were destined to enter; similarly, in referring to them as the smallest nation on the face of the earth, the book of Deuteronomy (7:7) says they were badly outnumbered by the inhabitants of the land. The book of Numbers (3:43) records the number of first-born Israelite males of all ages as 22,273; to have so few first-born males in a population totaling in excess of two million would have required a fertility rate of many dozens of children per woman—a phenomenon unmentioned by the Torah and not evidenced in any family lineages from that period in other ancient Near Eastern sources. Besides, an encampment of two million—equivalent to the population of Houston, Texas—would have taken days to traverse. Yet the Torah (Exodus 33:6-11) does not remark upon that, either, instead describing Israelites routinely exiting and returning to the camp with ease. Nor does it register the bedlam and gridlock that would have been created by the system of centralized sacrifices mandated in the book of Leviticus. In Exodus 15:27, moreover, the Israelites are reported camping at a particular desert oasis that boasted 70 date palms—which, for a population of two million, would have to have fed and sheltered 30,000 people per tree

ב"ה Shalom The premise upon which I base my answer to you, is the principle of the Torah which was received from Heaven and since it was given there has been an unbroken chain of the transmission of the Torah both written and oral. This is a tenet of Jewish faith. It is on this basis that we now try to understand the Torah and explore the commentaries and their explanations. Your question was multi-faceted so I would like to focus just on the multiplying of the Jewish people. According to our oral tradition each mother gave birth to sextuplets at each birth. Now assuming that each family had only 6 children while in Egypt, that means each generation in Egypt was 3 times bigger than the previous one. If we minimize the stay of the Jewish people in Egypt to 210 years, and if we calculate each generation as 30 years that means there were 7 generations of children. So if you take 6 children with the exponent of 7 generations and then multiply that with 70 people who came to Egypt we are talking about what I believe is called in mathematics exponential growth. However, there is much more to be discussed on this issue.For example, the Torah also mentions that a certain percentage of those in Egypt died during the plague of darkness,and that is something that also needs to be calculated and properly explained. However not everything can be covered in this limited concise answer forum. Have a Happy and kosher Pesach