#1
Ok so the sound is a crowd yelling. The best way for me to explain it is this video http://www.youtube.com/watch?v=UkQ124B9X6Y go to about 1:58 and you'll hear the crowd yelling part. There's got to be an easier way than recording a ton of people yelling the same thing right? Maybe some harmony software or something, anyway let me know if you have a clue as to how i could emulate a crowd yelling
#2
Best way is to get four or five people (even more if you can) into a room and then record multiple takes. There's not any software that you can cheat your way to the same effect with.
#3
^Thats your best bet. The more layers you add, the bigger it will sound.

Also, that red font is rather distracting.
#4
Pink Floyd did it on "Another Brick On The Wall".

5-6 children recorded several times..