I haven’t a clue what I’d have called it myself.
I think Dossier is a decent name as it fits the wartime theme well. The only other thing that comes to mind are the repeat references in the Dreddverse that many of MC-1’s files were lost during the Apocalypse War.
Perhaps something like
Apocalypse War: The Lost Files or
Lost Records might have worked, if the stories were bookended with present-day-Dreddverse chapters featuring an archivist of sorts still working through the backlog, and discovering all these untold stories from old reports as they do so.
In fact, I read a story recently featuring something similar;
The Big Lie, Prog 2224, where a cit is sentenced to archival duties to make sense of all the Department’s unsorted missing persons paperwork from Necropolis. Perhaps there’s the start of the next book!

Re: the chapters, certainly wasn’t a problem - For the most part it reminded me of the short Prog chapters in the original story and made for easy reading, going through a couple chapters a night!