Aharon - we addressed many of the points you raised in your question in our Insights to the Daf, which I include below.

Kollel Iyun Hadaf

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Eruvin 53

1) THE DIFFERENCE BETWEEN "ME'ABRIN" AND "ME'ABRIN"

QUESTION: The Mishnah (end of 52b) describes how we "extend (Me'abrin) the cities" in order to determine the boundaries of the Techum Shabbos. The Gemara says that Rav and Shmuel argue whether the word "Me'abrin" in the Mishnah is spelled with an Ayin or with an Alef. According to the opinion that it is spelled with an Alef, it means that we extend the city by "adding appendages to it" (from the word "Ever," limb). According to the opinion that it is spelled with an Ayin, it means that we extend the city like the body of "a pregnant woman" (from the word "Ubrah," pregnant).

Rebbi Yochanan says that the one thing that he learned as a youth from Rebbi Oshiya was that the word "Me'abrin" is spelled with an Alef.

What difference does it make how the word is spelled?

ANSWER: The TORAS CHAIM explains that how the word "Me'abrin" in the Mishnah is spelled has a practical Halachic ramification. The Gemara later (55b) says that a group of huts does not qualify as a city in order for its Techum to be measured from the outermost hut, because huts are not considered permanent dwelling places. Rather, each hut is viewed as independent and has its own Techum. What is the Halachah when such huts are located on the outskirts of a real city (that is, within 70 2/3 Amos of the city)? Are those huts considered the border of the city from which the extension is measured, or are they not considered part of the city, since they are not permanent dwelling places, and the city's extension is measured from the last permanent house in the city?

According to the opinion that "Me'abrin" is spelled with an "Alef," the huts do not qualify as part of the city. Just as a limb is a permanent appendage on the body, so, too, the houses from which we measure the extension of the city must be permanent. On the other hand, according to the opinion that "Me'abrin" is spelled with an Ayin, the extension may be measured from the huts, because a temporary dwelling place suffices in order to determine the city's extension. Just as a pregnant woman's "extension" is only temporary, so, too, the extension of a city may be measured from a temporary structure.

2) CAVES, NIMROD, AND A NEW KING

QUESTION: Rav and Shmuel argue whether the word "Me'abrin" in the Mishnah (end of 52b) is spelled with an Ayin or with an Alef (see previous Insight). The Gemara cites three more arguments between Rav and Shmuel.

They argue whether "Machpelah" means that the Cave of Machpelah ("doubled cave") was two stories high, or that it was the burial place for "doubled" couples.

They argue whether Nimrod's real name was Amrafel and he was merely called Nimrod, or his real name was Nimrod and he was called Amrafel.

They argue whether the Pharaoh that reigned in Egypt after the death of Yosef was a new king, or he was the same king who made new decrees against the Jews.

Is there any Halachic difference between Rav's and Shmuel's opinions in each of these cases?

ANSWER: The TORAS CHAIM answers that there is a Halachic difference in each of the arguments.

(a) If someone tells his friend that he is selling him a "doubled" burial cave, according to the first opinion he is obligated to give him a cave with one plot above another plot. According to the second opinion, he is obligated to give him a cave that is large enough to hold four couples (like the Cave of Machpelah).

(b) One is not allowed to give his child the name of a wicked person. If Nimrod's real name was not Nimrod but Amrafel, then one may name his child Nimrod, but not Amrafel. If his real name was Nimrod, then one may name his child Amrafel, but not Nimrod.

(c) If someone tells his friend that he is selling him a "new" house, according to the first opinion he is obligated to give him a newly built house. According to the second opinion, he may give his friend an old house that was made to look like a new one.