Music Composers Unite!
Me like. Ambient yes, but when you take this path, you're almost moving past diatonic language and touching on spectralism, or something conceptually similar, which I think is a good path, done this way. I think you've kept enough of a solid footing here in conventional language to make it an intelligible "ambient" experience.
Are you familiar with, and if so, have you any opinions on the soundtrack to Eraserhead? It's incredible. Almost the entire duration of the film is immersed in near-subsonic, reverberating sounds. I've been strangely fascinated with and frightened by that soundtrack for years, but I'm not sure just why.
I will listen to the whole thing again after I come back from a gig, but for now (I'm at roughly 7 minutes mark): it works well but for the rain, I think. Something is wrong with the rain. Perhaps it's too uniform. I caught myself thinking "hey is that pink noise? oh wait, nevermind, there's supposed to be rain, right". At any rate it didn't work musically for me. I believe mixing it with another layer that changes over time (perhaps a bit more close-up recording, like rain splashing on puddles or drumming on a roof?) would make it fluid enough.