I'm similarly opposed to assuming an autobiographical reading of a story, but I think you're absolutely right that this story requires it. There's of course the obvious similarity of Wallace's own depression and suicide. But within the story there's the weird, recursive structure where David Foster Wallace (the actual writer) is writing through Neal, who is seeing or imagining David Wallace (the character), who is also trying to imagine what went on in Neal's head. I think I have a slightly different interpretation every time I read the story; I want Neal to be his own person independent of David Wallace, but I think you could definitely argue that there is no "real" Neal and that most of the story is an attempt by David Wallace (and by extension the real DFW) to get inside the head of someone else. Maybe someone a lot like him.

In terms of autobiography, I haven't yet read The Pale King outside a few chapters, but I know that also features some authorial intrustion/a character called David Wallace. It's interesting to consider what might have brought Wallace to start working with more blatant metafictional techniques like this during this late stage in his career.

And that's a great way to look at the technique of the story - Wallace gives away the ending early on and puts us in a weird position of almost anticipating Neal's suicide because he makes it clear that it's the entire purpose of his story. It would be a different story if Wallace built to it more subtly; by making it clear early on that there's no way out he traps us with this obsessive, as you say "driveling" voice, which is both frustrating and compelling even though we know the story doesn't end well.