tl;dr

Margo/Sergei time travel fix-it idea

After being shot and killed in his hotel room, Sergei Nikulov wakes up 20 years earlier, on the plane on the way to the US, where he’ll meet Margo Madison for the first time.

Maybe he considers defecting to the US on that first trip, but shit happens and also he realizes he and Margo being in the US and in the Soviet Union is what stopped World War III, so THAT has to happen. And by then she's already let him know about the O-ring problem with Challenger, so the catalyst for their whole tragedy has happened.

Maybe he realizes, even if he defects to the US, she won't be safe. They need a third option: Brazil. But he hasn't met his Brazilian contact. So he has to wait to meet him to try and set in motion them running away together.

And of course a further complication is how to convince Margo of this: She's on an upward trajectory at NASA, why would she leave? He tries but knows he can't resist the KGB at this point, he's managing to hold them off on REALLY compromising stuff, but pressure is mounting. He considered somehow making it a dead end, but he knows to keep furthering the relationship AND to meet his Brazilian contact he has to be going to those conferences and be in good standing with the powers that be. So it's a tightrope, and it's not clean.

The easiest way to get Margo to see the reality of the situation and the danger is to come clean... but then she might not trust him.

I really want to read this 🥺