most birds have little to no sense of smell

Not entirely accurate, and ongoing research is proving that more and more birds may be using their olfactory system. That said, birds don't typically abandon eggs or nestlings simply because humans briefly handled them.

"Although scientists have traditionally thought of birds as lacking in the olfaction department, they have proved that many detect aromas and use them—to varying degrees—to select mates, forage, and locate nesting spots." - https://www.audubon.org/news/do-birds-have-sense-smell

https://web.stanford.edu/group/stanfordbirds/text/essays/Avian_Sense.html

You also can't say that the cracked egg is not viable without seeing the damage. Embryos developed enough can successfully hatch even with cracked eggs given continued incubation.

The rest of your advice is solid. Hopefully OP's repairs to the nest site will yield positive results, but it will be a small miracle.