I can't wait for the book as well!
I have also a couple of questions, I hope they won't sound too silly:
1: You say that Bukowski was "very disciplined (...)about sitting down at the "typer" ". So far in my readings of his letters, I only found mentions about his drinking at the typer. So where is it mentioned that he was, in fact, sober at the typewriter?
2: I'm not sure I understood what you said about Bach and Beethoven. Was it about the way Bukowski wrote? Talking about "streams", I do remember him referring to his poems as "streams" or as "flow".
About Bukowski and spirituality: I wonder to what extend one can relate it to the theme of "waiting" in his early poem. We often find people "waiting" either for nothing in particular, or for something undeterminate, or, simply, death. I often felt this "waiting" thing gave a sort of metaphysical resonance to the poems, but I don't know if that's related to any spiritual tradition in general (well, maybe the Last Judgement, but somehow the idea of bukowski being a proper Christian doesn't sound so appealing to me^^).