2.
部員(buin) = the basket club's members
They are recruiting new members(new 部員), so ブインブイン(buinbuin) is a pun using homonyms of ブイブイ(buibui).
3.
ド is an adverb in this case.
ド = really/amazing/very/surprisingly/awesome, or etc.
迫力 is a noun, but it means "have a tremendous impact" in this case.
Kagami is tall and looks powerful, then Riko felt that he has a tremendous impact like a tiger.
4.
In my opinion,
Riko was explaining about the basket team and her opinion on Kagami, but Kagami underestimated Japanese's basketball skill, he also underestimated Riko's skill, then he thought her opinion wasn't unworthy of hearing, then he said "そういうのいいよ 名前書いたら帰る".
そういうの ≒ that/that kind of thing/like that, or etc.
(Riko's explanation in this case.)
いいよ ≒ refuse/no, or etc.
(I refuse to hear)
たら ≒ if/then/after, or etc.
↓
I gonna return home after I fill out the club sign-up form.