I like the sound of this song compared to the others. Specifically, I find myself loving the prominent guitar. There are a couple times I thought I heard it develop a vaguely rock-type melody.
As for the song, I agree that this song likely takes place in the extremely tense moments before her passing. Numerous points in the song feel like the boy is fearing her passing, equating it to what are essentially natural disasters that cause the world (or more accurately, his world) to collapse in various ways. Be it the disappearing wind, the scorched earth that appears during summer, and the fact he emphasizes the world disappearing. I take that as him equating this girl’s existence to every facet of his being. Without her, his life literally means nothing, and considering Bokura no Koi, and like you mentioned, track 8, I can definitely believe that to be the case. On a side note, I feel the lines “It’s a dream too painful to watch / It’s gonna be for a little while longer” strongly suggest that she is fading away.
As for the “warm dream”, I could see that being the point where the girl is finally fading away. After all of this emotional build-up and concern, the actual event numbs him because he had been so thoroughly expecting it.
I’m a bit curious about what the “dream of blood stream” is. Does this represent her sickly condition, perhaps?
The image, most definitely of the girl, I see as the boy’s mental picture of her. She seems almost a divine figure, with the mysterious emblem on her top and clouds swirling behind her. It connects to song’s emphasis on how tantamount she is to the boy’s feelings of happiness and contentment.