I don't have the exact details. It might be that she passed away or maybe she just wasn't a big part of the story. You'd need to explore the plot further to find out.
Well, in the 'kids lost at Sam's Club' story, it might be that the parents were busy looking at some items and didn't notice the kids straying. Sam's Club is a big place with lots of aisles. The kids could have been trying to find their parents on their own and got lost in the process. It's a scary situation for both the kids and the parents. Usually, the store staff would then be alerted and start looking for the lost kids.
It could be that Sam found out some dark secret about Dean that he couldn't overlook. For instance, if he discovered that Dean had made a deal with a really evil force in the past to save Sam's life, but in doing so,Dean had unknowingly put many others in danger. Sam, with his strong sense of justice, might feel betrayed himself first and then in turn betray Dean to set things right.
The plot could center around the emotional journey. Sam may experience a range of emotions from joy to fear. Danny could be there to comfort and encourage. They might also face difficulties such as financial concerns. For example, they'll need to think about buying baby stuff, finding a bigger place if needed. And as the pregnancy progresses, they'll have to start thinking about Dani's future, like education and what kind of life they want to provide for the child.
It could lead to a lot of relationship changes. Maybe their friends and family in the fanfic world would have different reactions, either supportive or against it.
It could be related to some sort of power struggle. Suppose there's a power or ability that Sam has that Tucker wants, and he believes the only way to get it is by getting rid of Sam. Another possibility is that Tucker has been influenced by some dark force or entity that has compelled him to do this evil deed. This could add an element of the supernatural to the story and explain his otherwise out - of - character behavior.
In fanfics, all kinds of scenarios are possible. Just because it's written doesn't mean it adheres to the original canon. Maybe the author wanted to explore a unique relationship dynamic through this pregnancy plot. However, without reading it, it's hard to say more about it.
I don't know who Sam is without reading the 'kings fund sam's story'. Sam could be a patient, a researcher, a staff member or someone else related to the Kings Fund.
It's hard to say for sure. It could be that new characters were introduced or the main character faced some major challenges that changed the course of the story. Or perhaps there was a big reveal that shifted the entire narrative.