Sha'alvim: Who's right?

I was recently reflecting to a friend on the fact that many Israelis refer to the yeshiva located in the neighborhood of this ancient Danite city as Shalabim, while the American literature for the yeshiva calls it Sha'alvim. What do the pesukim call it?

1) Yehoshua 19:40-42: To the tribe of the sons of Dan, by their families, went forth the seventh lot. And the border of their inheritance was Tzor'ah and Eshta'ol and Ir-Shemesh. And Sha'alabin and Ayalon and Yislah.

2) II Shmuel 23:8,32: These are the names of the warriors of David: Tach'kemoni who dwelt in Sheves, head of the three; he is Adino HaEtzni, who killed 800 corpses at once... Elyachba HaSha'alvoni; the son of Yashein, Yonasan.

3) I Divrei HaYamim 11:26,33: And the warriors of the soldiers: Asa'el, brother of Yo'av; Elchanan son of Dodo of Beit-Lechem... Azmaves HaBacharumi; Elyachba HaSha'alvoni.

4) I Melachim 4:7,9: And Shlomo had 12 officials over all of Israel, and they fed the king and his household; one month of the year was it upon each to feed... Ben-Deker in Makatz and in Sha'alvim and Beit-Shemesh and Eilon-Beit-Chanan.

If I understand my dikduk correctly, which I don't, the bet is d'gusha in the passuk in Yehoshua in order to seal up the preceding necessarily closed syllable containing the t'nu'ah k'tana of patach, while the bet is rafah in the passuk in Melachim because it is not needed for this purpose (as the preceding syllable is sealed up by the lamed).

My first recollection was that Israelis called it Sha'albim, in which case I would have noted how this diggush seems to follow a general pattern found in similar words - Chelbon (egg white), 'Elbon (shame), Kalbon (see Shekalim 1:6) [there must be a more general rule, but I can't quite put my finger on it right now], but I now question my recollection, and have emended the post accordingly.
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