"I remember so little about the party, it's as though I never went." 私はそのパーティーについて、"まるで行ってないかのうよう"に少しのことしか覚えていない "He knows so much about the job he's applying for, it's as though he already works there."　彼は応募している会社の仕事について、"まるでもうそこで働いているかのように"よく知っている。 "it's as though" in Japanese is "まるで～のように"

"I remember so little about the party, it's as though I never went." If I translate this wordly, it does not sound like Japanese. So I would say, this might be more Japanese although a logic has been changed a little bit. "そのパーティのことについてはほとんど覚えていない。行っていないのとなんら変わらない”と訳した方が自然だと思います。 "They spend so much time together, they might as well be married." 彼と彼女はいつも一緒にいる。まるで結婚しているかのようだ。

To paraphrase your examples, could it be: "He knows so much about the job he's applying for, it's [almost like that] he already works there." There's this 「～ようにしている」to suggest a tendency or resemblance in one's action. http://j-nihongo.com/younisiteiru/ or「に似てる」to suggest a similarity in behavior or action. http://ejje.weblio.jp/content/%E3%81%AB%E4%BC%BC%E3%81%A6%E3%82%8B These are my guesses. Occasionally there are phrases that do not have an exact match between English / Japanese. "It's as though" may be one of them.