TO #4. Not a snowball’s chance in hell.
Once a comet breaks up, that’s it. Each piece goes along the same tract but they never catch up and reunite as a single body (not enough magnetism or cocooning materials).
I saw the atmospheric holes/marks that the major pieces of Comet Shoemaker-Levy left in Jupiter. They went in, one piece after another (and must have done some real damage/major impact) on its surface because of the large dark areas (of gases/fragments/surface debris),that rose into the upper atmosphere from these crash-sites.
One day we might get a helluva meteor shower or even a ghost comet debris cloud, but not a recreation of the original body.
ghost comet debris cloud...
does that come after a zombie apocalypse?
;-)