"Deciphering" The Poem Fire Walk With Me And Its Mysterious Nature - Twin Peaks (Fire Walk With Me) 

When Hawk talks about the native american map, in contains cornstalks which are broken in one of the corners. He says that once they are broken and burned, they produce "black fire". This seems to tie in with the plurality of fire like you mention. Corn is also a symbollic reference to the treatment of native americans, especially the blood corn laws. Also, when the nuclear test is dropped, this is an example of another bad fire - it causes Judy to regurgitate Bob. I think Mark Frost's additions to the story are quite related to human beings bringing evil into the world, he's quite a politically orientated guy and twin peaks books are more orientated to that line of thinking. The idea of "intercourse between the two worlds" is also expanded on by Mark Frost with Jack Parsons and his occult sex magick rituals (he actually performs a sex magic ritual around the test site of the bomb before its dropped interestingly). Diane and Cooper's mechanical sex in part 18 of the return also seems related to that but I have no idea how. Ultimately twin peaks is a melding between Lynch and Frost, so it's interesting to see twin peaks as a deep dive into the nature of reality and balance, represented through abstract cinema.