I also agree about the other paragraphs, most importantly the part about D of F not being an absolute.
I view D of F as the area which for ones intents and purposes appears as sharp as the plane of critical focus, not simply as the area which appears acceptably sharp. To use your term: the "acceptable unsharpness" matches between the plane of focus and the areas that simply appear sharp.
Like you said, in the same way that FL and distance from subject indirectly affect D of F in the camera by affecting magnification, print size and viewing distance indirectly affect D of F by affecting magnification when looking at the pix. A tiny print has less D of F under a loupe. A big print has more D of F from across the room.