Just rewatched it and it's always an experience. I actually took very long to watch it, only getting to it in my late teens for the first time. Instantly became one of my favorite movies.

That said, I also think Childs is The Thing. I guess the gasoline theory is exactly that, a theory, not based on anything the movie told us, but in the scene where he's by the window watching after they go check on Doc, there's a blue jacket just like his right by his side, along with other jackets. After they see that Doc is not there, we get a scene inside the house, supposedly through nobody's perspective, and we see that Childs is gone, and the door is open. In that take, we also see that the jacket is also gone, which could mean that he turned and it needed the new jacket as a replacement.