Parasha division in the Chumash

B"H Dear Rabbi, Who was responsible for dividing the Torah into the Parashot? Is it Esra Hasoffer? What was the method or logic that he used to determine the division among the different Parashot? Also, I was told that the Chapter division in the Torah was actually done by a Christian named Jerome Vulgate who actually lived in Israel many years ago. Although this division does not have any religious significance, it raises the question why Jews today are still using the same Chapter division? Is it for convenience? Thanks in advance for your help.

The word "parsha" has more than one meaning. The most basic meaning is the division of the written text with breaks in the writing on the parchment. This division is essential to the kashrut of the sefer Torah and is included in the tradition passed down from Moses.The second meaning is the division into weekly portions. This division is according to custom and sometimes varies- there were places in Yemen for example where Parshat Hukkat was not read all at once on one shabbat so as not to read about too much sadness- the deaths of both Miriam and Aharon- in one week. There had been a tradition in the Land of Israel to complete the reading of the Torah only once every three years (Megilla 29b), but the accepted minhag is to complete the Torah reading on Simchat Torah every year (Rambam Hilchot Tefilla 13 1). Ezra arranged that the division into parashot be such that the rebuke at the end of Vayikra be read before Shavuot and the rebuke at the end of Devarim be read before Rosh Hashana. Accepted custom arranged the reading so that other parashot as well are read at specific times of the year- for example VaEtchanan after Tisha B'Av. The third meaning of the word "parsha" is the internal division of the weekly portion into seven. Traditions here differ but certain rules are standard (Rambam Hilchot Tefilla 13 5; Shulchan Aruch Orach Chayyim 428 5). The division of the Torah into chapters is not halachic but a matter of convenience only.