While it's impossible to say with certainty, the "seriousness" with which Cage discusses his own work seems to have an element of tongue-in-cheek humor (the kind that he'd never openly admit). I had watched an early video of Cage performing "Water Dance" in which he welcomed laughter, but the tone of his writing is entirely serious. He gets nearly hyperbolic when describing how all records should be smashed because they're useless (76). Even his diagrams (81, for example) seem to be a type of joke with no clearly understandable means of interpretation.
In Dworkin's list of unheard music, he writes (of Cage's 4'33" score), "it sounds pretty good even in transcriptions." This must be a joke--because it nothingness doesn't need to be transcribed. I think everyone kind of enjoys this sort of joke. In fact, many of Cage's anecdotes between sections in his book are plays on words or humorous mishearing/misunderstandings. When Dworkin denounces Mike Bott's silent song as "third-rate," this also seems to be part of the joke (how is one person's silence interesting and another's not?). Maybe I'd have to "hear" it to understand.
In the video of the "full orchestral" version of 4'33", I feel like this strange blend of seriousness and humor lived on even beyond Cage's death. Would it have sounded different if there were a few fewer bassoons? Well maybe, but no more than it would have if it was done out of cold season. I think that people really enjoy this kind of joke--the knowing goofiness of doing something unexpected. At the same time, everyone seemed very pleased with the results--to hear such a great quiet in a place known where usually filled with more distracting noises. So while my answer to the "is he serious" question is a bit unclear, I feel like sense of discovery that Cage inspires is entirely serious and worthy of attention (but at the same time, it's occasionally ridiculous).
Question 2.
How should one interpret a reading of Cage's lectures/poems when on the page (particularly pieces that are meant to be accompanied with music, or other voices, or visual cues)? Is what's on the page sort of like reading a film script (not the important thing, really, but the thing that makes the important thing), or is it different for Cage.
I'm including a picture here of Mortal Kombat's Johnny Cage, because I think that's helpful to answering these.
And though this isn't part of the questions--would anyone be interested in a Zaireeka listening? I haven't done one in years and reading about Cage's work and the other "Unheard Sounds" (particularly Vitiello installation with the low frequencies and Cage's Imaginary Landscapes) reminded me of how amazing an experience it is (for those who don't know The Flaming Lips, it's a four disc album where all four discs are meant to be played simultaneously--some tracks contain frequencies at the borders of human hearing, the high and low all at once, it's very disorienting and enjoyable).
Here's a video of Wayne Coyne, explaining very little, but getting ready to play one of these.