1. Do we know where Nunia is?
2. It takes 18 minutes for an average person to walk 2000 amot.
An amah is said to be between 1.5 and 2 feet.
Hence, it takes 18 minutes to walk between 3000 and 4000 feet.
Conisdering that a 3 mile per hour pace is considered slow,
18 minutes to 4000 feet seems on the slow side.
3. From the give and take between Rabba and Rav Chisda,
is the following true:
Rabba: Ho'il is min HaTorah
Cook on Yom Tov for Chol - no malkot
Shabbat and Yom Tov are two kedushot
You can cook on Yom Tov for Shabbat because of Ho'il
Rav Chisda: Ho'il is not min HaTorah
Cook on Yom Tov for Chol - malkot
Shabbat and Yom Tov are one kedusha
You can cook on Yom Tov for Shabbat min HaTorah because of one kedusha
If the above is true, then who does the Rambam follow who paskens
1) Shabbat and Yom Tov are one kedusha min HaTorah
Yom Tov 6 1
2) Cook on Yom Tov for Chol - no malkot
Yom Tov 1 15
Sidney Gottesman
1. I am not aware whether or not it is known today where Nunya is (see Insights).
2. You are correct that at a normal pace of calm and not hurried walking, a person walks one Mil in 18 minutes, or about 3 1/3 feet per second.
3.
(a) Your question is very good. It is asked and addressed by the BEIS YOSEF (beginning of OC 527). The Beis Yosef proposes that the Rambam is working with different assumptions than the ones which you wrote. The Beis Yosef says that according to the Rambam, the opinion which holds of "Ho'il" also holds that Shabbos and Yom Tov are one Kedushah (although this certainly is not implied in the Sugya).
(b) The MAGEN AVRAHAM (ibid.) takes issue with the Beis Yosef's explanation of the Rambam. He argues and says that the Rambam's opinion in Hilchos Yom Tov 6:1 is not that Shabbos and Yom Tov are one Kedushah, but that the Rambam agrees that Shabbos and Yom Tov are two Kedushos. However, this is certainly not implied by the Rambam's words, because the Rambam clearly differentiates between one who bakes on Yom Tov for the weekday and one who bakes on Yom Tov for Shabbos (No evidence as to the Rambam's opinion on this matter can be drawn from Hilchos Yom Tov 1:19, as is clear from the Sugya he is discussing there.)
Furthermore, it clearly seems from the words of the Rambam there that he does not hold of "Ho'il," and baking on Yom Tov for the weekday is Asur mid'Oraisa; the Rambam thus contradicts what he writes explicitly in Hilchos Yom Tov 1:15, a problem dealt with by the Hagahos Maimoniyos (in the end of his comments).
(c) Rather, it seems that the clearest way of understanding the Rambam is the approach suggested by the KEREN ORAH (end of Shabbos 22b), who explains that the Rambam holds that "Ho'il" makes one Patur from Malkus, but the Isur Aseh against cooking for the weekday remains ("Lachem" teaches that it is permissible to cook only "for you" and not for gentiles or for weekday use).
That is, when the Gemara derives that cooking is permitted on Yom Tov "for you and not for gentiles," it rescinded that which it writes at the beginning of the Sugya, that according to Rabah "Ho'il" permits cooking on Yom Tov for the weekday mid'Oraisa. Rather, in the Gemara's conclusion, the Gemara maintains that it is forbidden to cook on Yom Tov for the weekday mid'Oraisa, but there is no Malkus. This must be so, because otherwise how could the Torah prohibit cooking for gentiles or for Gavoha even though it is "Chazi l'Orchim!" (This latter is a problem which the Rishonim address, see Tosfos, end of 46b.)
Best wishes,
-Mordecai