The PCs are all of the same generation, from the same shtetl, all Jews, none of them rich. That's the game's frame.
The game has three Acts, each of which can take place over one or many sessions. In each act, there's a social matter at stake, as well as external threats, including one major existential threat to the shtetl and its inhabitants (that's the piece that's from Storming the Tower; a town, where the characters all belong, and a threat to it that will drive them to action). The social stake and the major threat work together to form the Act's countdown clock.
In the First Act, the characters are 14-18 years old, and the social stake is: will they marry? And if so, whom will they marry? This is (as per the other thread) a milieu in which arranged marriage is common, so the PCs have some, but not total, agency regarding who they marry.
Characters start with a First Act playbook, which is called a Nature. The Natures aren't professions or collections of badass skills. Their moves include how you get experience, what gives you or deprives you of emotional sustenance, as well as a couple of cool things you can do. The PCs are kids at this point, so the Natures have to do more with "who are you?" than with "what can you do?"
The Natures are: The Dreamer, The Charmer, The Studious One, The Enterprising One, The Rascal, and The Dutiful Child.
When the external threat is resolved -- either averted, altered, or the doom comes to pass -- and the social stake is also resolved, the act ends. In the case of the First Act, I think it's something like: as soon as one PC is betrothed, we enter some kind of now-or-never marriage resolution session (like Monsterhearts' Season Finale) following which the act comes to an end. Or, if the characters have all decisively avoided marriage, that would end the act too. In any event, their fates are clear.
Between the First and Second act, twenty-some years pass. A series of inter-act mechanics -- which work like love letters or the Operator's gigs and Hardholder's "how's your hardhold doing?" start-of-session moves, but on a grand scale -- summarize the intervening years. So now you're in your mid-thirties, early forties.
You get a Second Act playbook, added onto your First Act playbook. It's called a Calling. In Dungeon World terms, it's a compendium class. But there's a twist: what Calling you get depends on what you did in the First Act. So if you killed someone, for whatever reason, in the First Act, you may not be able to avoid becoming the Soldier. If you made peace between rivals, that may set you up to be the Matchmaker. So you end up, in the Second Act, with a Nature and a Calling.
The Callings I've got so far are: The Midwife, The Matchmaker, The Soldier, The Gonef (criminal), The Klezmer (traveling musician), The Sorcerer, The Villager, The Soldier, and The Talmudist.
Max one PC for each, except for the Villager, which is the catchall if nothing else triggers for you.
(The first two are reserved for PCs with female gender roles, the last two for PCs with male gender roles. But note that you can potentially change your gender role -- after all, Yentl is one of our source texts. There's a special move for "when someone who saw you naked would likely conclude that you were [the other gender]" -- basically, this puts you at great risk but is also an xp factory, when you're in situations requiring you to manage your secret).
In the Second Act, there's another external major threat, dissimilar to the first (so if the First Act's problem was a dybbuk, the Second's might be a Cossack uprising). The social stake is arranging your children's marriages (obviously some PCs won't have had children, but their social stake is still based on the same set of cultural expectations; you have no children, so who will say Kaddish for you?)
I'm a little fuzzier about the Third Act, when the PCs are in their sixties. It may have Third Act playbooks, which may be called Destinies and might include Kabbalist, Tzaddik, Matriarch, Gvir (wealthy person)...? Its external threat may echo or unite the threats from the first two acts. It may be about facing death, in terms of the social stake. (If it doesnt' come together, in the end, two acts would be okay, but three seems better). Again, between the Second and Third acts there would be a set of summary moves for the intervening twenty-odd years.