You're welcome! I spent some time reading the discussion on reddit after each episode, and some of the explanations there were super useful.
So the show started with four "main" families:
Nielsen - wiped out, all resulted from the knot. Technically, Jana, Ulrich's mother, exists, but is likely not relevant to the 6 characters at the end).
Kahnwald - still exist, but as Ines never adopted Mikkel, she probably didn't have children so this line died out.
Tiedemann - Doris and Egon have Claudia, but she ends up marrying Bernd (who has always been Regina's father in all timelines), we just didn't know until the end.
Doppler - Regina as we found out, and of course Helge and Peter. There's no Charlotte, so their children don't exist.
Katharina and Hannah are only part of the families by marriage, so their ancestors are still there too.
I think you have the main list of people that would not have existed - Silja doesn't exist as she's the result of the time travel, and Bartosz doesn't seem to exist either (though he could, see below). Their children Agnes and Noah also don't exist, thus the Nielsens and Charlotte/Elisabeth/Franziska).
Even though there no loops anymore in the real world, I'm assuming that Alexander's life still occurred the same way. I don't think his intention was ever to stop in Winden. If you remember his introduction, he had been shot and was running through the woods, came across Regina and saved her, then fainted from the wound. Regina ends up helping him, and it starts their relationship. It's at that point that he decides to stay (he buries his original passport after meeting her) and then gets the power plant job.
Without meeting Regina in the forest, he could either die from the wound, or keep running and end up somewhere else where he either is caught or lives under the assumed name somewhere else. I believe that without the Unknown Trio the power plant isn't built (no cooling towers in the background) so no job for him either. So while Bartosz could exist in theory as both his parents exist, they don't meet so he doesn't. This part was quite sad for me - it was clear that Regina and Alexander really loved each other and had a good marriage, but Regina does seem happy in the end.
Check out the official website: https://darknetflix.io/en/family-tree
I didn't discover it until after I finished the show, but it is really well done, and you can choose what episode you're on to prevent spoilers. Just a tip, the site allows you to click on a character and see their story chronologically. When you get to the end with Jonas, the website will "dissolve" the paradox characters and leave everyone else.
If I remember correctly they were asking him for the keys? And I think this is the same episode where they kill Jasmin, Claudia's secretary. And then at the end, they give the keys and booklet on the Power Plant Volume Control to Eva. I think the Trio uses these items to cause the "accident" at the plant in June of 86 which causes all the loops/time travel.
I have a theory based on something Claudia said, which is that Regina can live in the real world because she is not descended from the loop. Within the loop, she always dies. So my theory is that this applies to everyone who can exist in the real world - Bernd, Helge, Peter, Egon, Claudia, Regina, Bartosz, Hannah, Katharina - all are murdered within the loops. Everyone else lives, but they're all the paradox characters. Mikkel commits suicide so I won't count him, and I'm not counting the kids that were killed because of time travel. Not sure if I missed anyone else? I'm not sure if I should count Bartosz, since he could exist, but technically doesn't.