Why is there a mitzvah to guard the Temple even when there is no fear of enemies or thieves?
The Rambam states explicitly that the guarding is an expression of respect (כבוד) for the Temple — a palace with guards is far more impressive than one without, regardless of any security concern.
Question 2
How many total guard positions were maintained in the Temple, and how were they divided?
There were 24 guard posts in total: the priests stood watch in 3 places (Chamber of Avtinas, Chamber of the Spark, Chamber of the Hearth), while the Levites covered 21 positions.
Question 3
If a priest on watch had a seminal emission during the night, what was the correct procedure?
The priest would descend through an unconsecrated underground passage to immerse himself. Since the passageway opened to non-consecrated areas, there was no prohibition. He would then return and sit with his fellow priests until the gates opened at dawn.
Question 4
What authority did the Officer of the Temple Mount have over a sleeping guard?
The Officer of the Temple Mount would strike a sleeping guard with his staff. He was even permitted to burn the guard's clothing — an exception to the prohibition of destroying valuable items — in order to ensure proper guarding of the Temple.
Question 5
How was the pre-dawn inspection of the Temple Courtyard conducted on Sabbath eve, and why?
On Sabbath eve, the priests did not carry torches (which would involve carrying fire on Shabbat). Instead, they navigated by the light of candles that had been lit before the Sabbath began — since it was possible to use pre-existing light, no prohibition was violated, even a Rabbinic one.