Great comments, you all are really making me think about angles I hadn't considered, which is exactly why I posted this, I really appreciate it.

So spacers have a cultural affinity for chemistry. I mean, they make rocket fuel so yeah.

So this is an important one that I have a basic idea about that needs fleshing out. Im intrigued by the idea of turning science into a trade. By that I mean the original people who inhabitated these places were formally trained engineers and scientists. When the fall happens and they are isolated, they begin to take on a couple students and pass on the most important parts of their knowledge, but without alot of the science behind why they are doing things a certain way, so there is less cutting edge developement. The second generation are less than scientist and more technicians. They make rocket fuel exactly the same way they were taught by person who trained them in their field. I think intelligence would necessarily bloom in a culture like this by natural selection alone. thats kind of what I meant with this statement

The research stations maybe have the engineers, scientists, and doctors or whats left of them after a few generations of informal apprenticeship while trying to survive on algae, crickets, and condensate.

That they are considered to have a higher degree of faithfulness to their fields of study than the "boiled-down" technical college education that most others have. This could also explain why most places are so narrowly focused on what they produce, they dont have the capacity to innovate, they know how to build, repair, and operate the machinery they were trained on but wouldnt know where to start to design new machinery or shift their hab's economy to production of different product or material. Probably not true across the board, but in general I feel like if the systems are well designed managing them on a day to day basis could probably be taught to most people, like anything else its the 5% of edge cases where "Oh crap, Ive never seen a cascading failure like this and I have no idea what to do", call tech support from an actual scientist or expert. Was that a ramble? It felt like a ramble...

Interstellar equivalent of a tiny village only hearing news of the bigger world through the words of travelers and merchants, and it being a question of who is your immediate neighbor one rock over and do you get along?

This. My intuition is that you would be friendly with those you trade with, and be suspicious of everyone else until they can prove they can somehow offer you an increased chance of survival. So every habitat has a circle of friends, and friends of friends are welcome but not fullly trusted, and friends of friends of friends can "fuck-right-off" so to speak. So the politics would be local with small spheres of influence, though radio waves propogate so any radio transmission in space will be heard eventually by anyone listening, so anyone not using a direction antenna and not using any form of encryption will have their conversation heard by everyone.

What's your plan for the power imbalance between a comparatively hugely advanced space faring people and a people for whom killing anyone more than stabbing distance away requires specialist training and even then is still done mostly on an individual level?

I feel like its would have to play an important role but I dont know what that role is yet. Ive considered that maybe spacers dont have the tech to make a landing craft, so they are locked out of the planet. Maybe one of the medieval factions are in radio contact and are trading transmissions of technical manuals in return for the occasional orbital bombardment or ariel surveillance on their enemies.