To be fair, whether Ripley defeated Big Chap or not, the Xenomorph has been showed to survive in the outer space, if Isolation is anything to go by, which Fede is clearly inspired by.
Maybe it just went into some sort of freeze/sleep mode, like Kars in Jojo's Bizarre Adventure.
But i think you can't call it the Perfect Organism if it doesn't survive in space, so i am more worried about Big Chap is found in the first place, than it necessarily surviving in outer space.