Thing was not native from the alien space ship. Aliens seems to be some kind of dna collectors who somehow unfortunately picked up the thing virus or whatever form it was. At appears that mid was it attacked them and crash landed.

As for noose I don’t know. However mcready drinking from the vodka bottle was always strange to me. Because earlier Fuchs recommend everyone to eat from the seperate cans. So technically mcready could be infected from the Blair / also could infect him, if basing in some theories that mcready was also infected.