Do you read that as Beckett saying that he is writing not from “nothingness” in an existential sense but from “a place without intellect or the observation that could declare something to be ‘nothing’ or ‘something’”? That latter seems likely.
I’m not sure if I quite understand your question (and this uncertainty of mine might very well stem from my own unfinished thinking on the subject …), but here is what I want to say for now:
On one level, as seen in the previous cited interview, Beckett seems to want to distance his writing from strict (restrictive & limiting) philosophical readings. By appealing to feelings he is suggesting some kind of subjective enigma in the centre of his own writing.
But we all know that Beckett read a lot of philosophy. And also; that a lot of his writing is in direct (and/or indirect) dialogue with previous thinkers and writers. Sometimes mocking, sometimes more as a way of trying out philosophical statements and positions in a literary universe.
Still, the previous decades of Beckett-research have been very theory driven. And maybe, in fear of becoming personal (doing soft-science), researchers have forgotten to investigate the more emotional aspects of his art. For example: is nothing an idea or a feeling in Beckett’s literature. And if we can agree that it is both, what more can be said about the emotional source of nothingness? How is it written out – in praxis – so to speak, and what can it tell us about … ourselves?
sub rosa 
What I was wondering was this: if the ‘self’ that Beckett was using as his point of observation did not include the cognitive tools of philosophy (they were apprehended or outside of this core area), would philosophy then, by the very definition of the self set by Beckett’s boundaries, be ‘nothing’ if this self were observed by the cognitive tools of philosophy, whereas philosophy would be the ‘nothing’ if viewed by this self. At the same time, if this emotional space, this ‘self’ that cannot include philosophical material in its core and thus can only physically apprehend it, with emotion being the replacement for delineated cognition, looked out at the world, it would see emotional and bodily action rather than worked-out philosophy or worked-out complex social dynamics such as politics, history and so on, with the same nothing-something interchange. Is this not the Kultur-Civilisation divide of the 1910s, embodied as the Great War, and re-embodied in the violent, depersonalizing and emotional struggles of World War II, as well in the atomic and quantum science and technology of the period, all as physically experienced by a profoundly sensitive human instrument ie Beckett? Is the divide then the “event horizon” of a black hole, another expression of this philosophical space? If so, there are some powerful questions: what is this quantum horizon? What is, or what has made, this black hole? What grief or trauma or power is there at the core, so condensed that everything that comes into its orbit is either absorbed or cast out as deconstructed light? One could ask the same of Munch’s Scream. Sartre would, I suspect, have called it evil, but I think that is just another deflection, made out of great pain.
Thank you Harold! Obviously this is stuff for longer meditation, so at the moment a short note will have to do:
I do not read Beckett in line with the existentialists, mainly because I understand him to have a very different view and use of language. And there is a nihilism in Beckett which seems to me to be very, well … I am tempted to say constitutional, for Beckett. One see this maybe clearest in his Trilogy, where his project is not to construct but to deconstruct the self. Not because he want to show us what happens to a person (Molloy/Malone/The Unnamable) in a cruel world, but because this deconstructed/demolished – self, is a truer image of the self.
His theme, one could maybe say, is existential, but he is not an existentialist.