for what it's worth, they show an enlarged clock that is, on the image, 1 mm across -- I've seen much sharper and clearer detail than that on 1 mm of a Minox negative after being blown up to a 4 by 5 print and remember a minox negative is is only 9 by 12 mm, on asa 25 and even 100 film, so I'd say that resolution of the sort they're discussing is certainly possible today, but you have to have perfect conditions. Them saying those images equal 140 gigs today really doesn't mean anything -- people try to compare pixel and grain sizes, but you're talking apples and oranges. Grain is on the microscopic level while pixels are not, so the comparison is only for giggles.
i don't understand yur last question =-- a 3D microscope will let the observer look at the same spot from two slightly different angles, you won't get real 3-d in looking at a flat image, but you will see the same spot from two slightly different angles and, thus, have a lot more information to make up the final image in your head, which will be clearer than a mere flat image.
mercury is part of the development process -- i don't remember the chemistry, but don't try it, highly dangerous. Modern deguerrans have other options.