The words are not related.
There is a root סככ which gives rise to the words סוכּה and סכך and מסך. This root has to do with covering/blocking, as you can see in Ex 25:20 (and the three words above).
There is a root סוכ that means smear/anoint, polish, whence the two examples in the OP (תסוך and סכת).
There is a root נסכ that means melt/spread, cast, pour ...
The Peninei Halacha basing itself on two instances in Shas, writes about the Yomim Noraim (7:14) the following:
שלושה סוגים של השתחוויה ישנם: השתחוויה גמורה היא כשהגוף שטוח על הארץ בפישוט ידיים ורגליים. קידה היא שהאדם נותר עומד על רגליו וכופף ראשו עד שהוא מגיע לארץ. כריעה היא שאדם יורד על ברכיו וכופף את גופו עד שפניו מגיעות לארץ (ברכות לד, ב; שבועות טז, ב). ...
Bava Metzia 60a:
א"ר אלעזר עדא אמרה כל באמת אמרו הלכה היא
Rabbi Elazar said: That is to say, every time a halakha is introduced with the phrase: Actually they said, it is an established halakha with regard to which there is no uncertainty.
(Steinsaltz translation and elucidation)
Yes, these headings appear in Hebrew manuscripts. Here are two of the most famous manuscripts with the heading for your psalm: למנצח אל־תשחת לדוד מכתם בשלח שאול וישמרו את־הבית להמיתו.
Leningrad Codex — dated to 1008/9 CE — right column, bottom paragraph is the beginning of the psalm.
Aleppo Codex — dated to ca. 920 CE — right column, bottom paragraph (it's ...
G-d did not command man to fill any specific geographic area, so colonizing additional area (on earth or elsewhere) does not directly fulfil any commandment.
Ramban explains "fill the earth" (וּמִלְא֥וּ אֶת־הָאָ֖רֶץ) as G-d's blessing to mankind to increase in numbers and populate vast areas; and "and subdue it" (וְכִבְשֻׁ֑הָ) as G-d's ...
Welcome to Mi Yodeya and thank you for sharing your fascinating question, Doug!
Rav Moshe Heinemann says in the name of his Rosh Yeshiva, Rav Aharon Kotler zt"l, that we are not supposed to travel outside of earth based on the verse in Tehillim (115:16):
הַשָּׁמַיִם שָׁמַיִם לַה' וְהָאָרֶץ נָתַן לִבְנֵי־אָדָם׃ The heavens belong to the LORD, but the ...
This is only a partial answer:
In the aforementioned time, Judaism had already spread out widely. Jews lived in Syria and Persia (today mainly Iraq), where Aramaic was the common language, in the Mediterranian areas where Greek was the common language, in Ethopia, where Geez was the common language and probably also in Arabia and Jemen where Arabic was the ...
As a general rule, all the letters of אהו"י are interchangeable (Ibn Ezra). One example I found with a quick search is Zecharya 11:13 where a yud replaces an aleph.
UPDATE: I went and found a few more examples:
Here are two cases where the same word is spelled with an aleph in Divrei Hayamim and a heh in Melachim, according to the Radak: 1 and 2.