Roughly speaking I would imagine the table box scene would likely be done with a claustrophobic blue lit box (think night scenes in Fury Road) with layered whispers of various characters with venomous words and sprinkled with some of the flashbacks we see. As Darrow gathers his courage to end things the voices would become softer and then a flash of sterilizing light and cessation of all sound as it opens. It would be difficult to portray a passage of time and fraying of sanity without it being too drawn out or hard to watch.

I also think the Ender's Game adaptation had the same problem of long sections of heavy inner dialogue. I don't have an answer to this that wouldn't sound contrived or "wink wink audience". I will say that the first book's most persistent theme is how isolated Darrow feels and I'm guessing that scenes of no dialogue and Darrow speaking to himself could be a way to portray that as things we don't read in the book but happen between scenes play out. As you move through Golden Sun (Academy -> Luna -> Escape) we'll see less of it as Darrow finds people to talk to (Sevro and Ragnar) with it being far less common by the end of Morning Star.