hi! first of all, i'm glad that you liked it. i'm sorry for how vague my answers will be, but i hope they provide some sort of closure.
it is intentionally vague, but i realize that's an unfulfilling answer. originally, it was intended to be fairly clear-cut that lera died at the end, but some things happened in my personal life, my viewpoint shifted, and i decided that i didn't want to release such a hopeless story into the world. i'm much happier having it be up to the player, and i hope that there is ample evidence for the view that she survived and was amalgamated into the building to lead a happier life, fully loved and part of something. i don't want her descent into the pit to be read as a suicide, at the very least.
i've always refered to nika as the "child" of the buildings-- she is a part of that family, and thus, as synecdoche, the building itself. yet, she still has independent thoughts and a seemingly human form-- she is not quite a puppet, but she's a mediator of sorts between lera and the family.
the gasoline is just a trap. the real answer to this is extremely boring, which is that i needed some sort of justification to lead lera into the building and have her stay there, and there is no deeper signifigance.
i guess the "i thought you'd be angry with me" comment doesn't make much sense in the context of the happy ending-- i wrote it after writing the true ending, to be honest. i can understand why it would be a bit confusing after the other ending.