Yes! I'm really impressed by how well all the details hold together, over seven seasons. The writing team did a great job of understanding (and remembering) the finer details of the universe they created, weaving everything together to create a coherent tapestry. I don't notice much contradiction over the seasons, but I do notice how well everything fits together, the storytelling constantly reaching back into its own history to draw out new nuance.
Yeah, the backstory with Kora really explains a lot about Jiaying and why she ended up volunteering at the same clinic as Cal - she was studying to be a doctor, Cal told us in S2, and had intended to return to Milwaukee with him to finish her training. Linking that story to the backstory about Kora's suicide suggests that Jiaying pretty much fled Afterlife after her daughter's death and tried to bury herself in a new life.
I wonder, though, if the village where she met Cal was the village she originally came from, her original home? I think it probably was, since Whitehall seemed to know where to look for her. How unfortunate that she returned there just as Whitehall was released from prison after so many years!
I think the only thing we know about Simmons's parents is that they exist and are still together, because they are always spoken of as a unit and she has them listed under the same number in her phone. When she thought she was going to die in S1 she told Coulson to tell her dad first, so he could soften the blow for her mum. The impression I got was that they are resoundingly normal people who would not understand the life Jemma leads in the slightest. Oh, and we know they live in Sheffield - Coulson talked about going to Sheffield to give them the bad news after Simmons got sucked into the portal in the S2 finale.
We don't really know much about Elena's family, either, beyond the cousin who died in her first episode and the sad backstory about her uncle being murdered that we got in S7. I would add Bobbi and Hunter to that list, as their only backstory was with each other, but they weren't really around long enough to be explored in depth.
On this re-watch for the first time I remembered to watch Age of Ultron in its proper place in the season, between 2-19 and 2.20 - I think that's the last real tie-in, isn't it, that is alluded to in the show? Other than a couple of vague references to Thanos in S5 that never got paid off, that is.