What does "fifty by fifty" refer to?
Rashi: It refers to the eastern half of the Chatzer, which was completely clear. 1
Hadar Zekenim: It hints that [Chatzer ha'Mishkan] is one part in 50 of Har ha'Bayis, which was 500 Amos by 500 Amos
The Mishkan took up thirty Amos by ten of the western half of the Chatzer, and twenty Amos on both its sides and behind it (on the west) were clear (Rashi). See also Ba'al ha'Turim.
Why does the Pasuk repeat the fact that the sockets were made of copper?
Rashi: Previously the Torah taught us that the sockets of the curtains were made of copper; now it is coming to incorporate the sockets of the screen.
The Pasuk states here that the curtains were only five Amos tall. According to those who maintain that the Mizbe'ach was ten Amos tall, Kohanim serving on the Mizbe'ach were plainly visible from the outside (which is not modest)!
Zevachim, 59b: That opinion holds that the curtains were 15 Amos tall. 1 The Torah means that they were five Amos above the height of the Mizbe'ach.
Da'as Zekenim and Hadar Zekenim, both citing Riva: The Pasuk states here that the curtains in the east were five Amos taller than the others. The others were 15, and these were 20. You are forced to say that the [Masach] in front of the [Chatzer of the] Mishkan was 20 Amos tall, like the height of the opening of the Heichal. 2 And if so, you must say that the curtains on each side of the Masach were 15 tall.
What forces us to say so? The Heichal was taller than the Mishkan. And there it discusses the opening, and here it discusses the curtain! Zevachim 59b does not distinguish; it implies that all the curtains were five, or all were 15! And it is a big Chidush that curtains of different heights were hung from a common pole - refer to 27:10:1:2*. (PF)
If, as the Pasuk states here, the Chatzer was only five Amos tall, then according to those who maintain that the Mizbe'ach was ten Amos tall, the Kohanim performing an Avodah on the Mizbe'ach, was plainly visible from the outside (which is considered lacking in modesty)?
Zevachim, 59b: In fact, the Chatzer was fifteen Amos tall, 1 and when the Torah writes here five Amos, it is referring to the five Amos that extended beyond the height of the Mizbe'ch.
And what 'pegs' is it coming to include?