受験便所 is for 受験生 I guess. So I guess it'd be on the third floor at a school.
I can hear the lyrics perfectly fine.
宇宙 Sunday = 息子さんは
中３で
受験便所 =
受験勉強してた
He talks about 夜食のカップヌードル... I thought he said 安くのカップヌードル the first time I heard it.
He also sings about how むうぅすっこさん was all sad about how his ワォかあさん わすれった'd his cup of noodles
