I took a crack at the weird credits:
プログラマ さだもん と がーふあんくる
Programmers: Sadamon and Garfunkel
(This one's fine.)
はかせ と その かよいづま
The Professor and His Long-Distance Wife
デザイナー あべる あべれば あべるとき
Designer(s): Fatty McFatfat
//あべる is apparently an alternate reading of 太る.
プランナー かある くらうざあ いのまた
Planner(s): Karl Klauser Inomata
サッキョク だんじり だんじり くむくむ
Composer(s): Danjiri Kum-Kum
//I think this name is a combination of Danjiri (from Danjiri Festivals) and Kum-Kum, the protagonist of a really old anime.
ガンバッタ みにもん ぼん おーちゃんず
Special Thanks: Minimon Bon Ochanzu
Masayuki "Thanatar" Kurinaga
//I think "Thanatar" is a reference to RuneQuest.
Damage Designer Kasaki
Vegetable Drinker Hirorin
Bunny and the Gang
As for the two item names, you're overthinking とくべつれいのふく. It's definitely 特別霊の服. I'd go all SaGa Frontier and translate it as "Spiritwear."
たまごだん is a bit trickier. As a suffix, 弾 is pretty generic. It can mean "bullet," "bomb," "flare," or even "grenade." More importantly, though, chicken eggs are said to stun or harm Jiang Shi. I would just go with "Egg" or "Hen's Egg" in this case.