This one was hard work, but at no point did I become completely stuck: steady crawling progress was always possible. I did come here for some hints, but took sustenance from early posts about it being a tough one, and finished under my own steam in the end. Just popped here to find a hint for the parsing of 3d, which I found thanks, and to see what the connection is between thematic items and the “writer”, and no one seems to know that. Perhaps we’ll all kick ourselves when the explanation comes out, but if it does turn out to be non-public connection that will be one negative point for me in an otherwise very enjoyable solve. Now going for a lie down!
btw, for me, the perimeter solves came late, with only one or two exceptions. Once the highlighted letters emerged, a very efficiently stored and sorted web site provided a ready set of hints as to what the candidate words for the solutions to the perimeter clues might be!