I know two of them!
#2 is "Anybody's Baby" by AnnieM. This is one of my all time favorite L&C stories, so I'm excited to be able to help others read it.
#3 I'm pretty sure you are thinking of Nan Smith's multi-part "Home" series. The premise combines the soulmates concept with the idea that Clark doesn't age the way a human would. But since L&C's souls are tied together, as soon as Lois dies (at a very old age), she is immediately reincarnated into a baby born at the same time, and Clark just has to wait ~20 years to find her to court her all over again.
The first one doesn't strike any bells, but hopefully someone else will recognize it.
