Mara: yes, hard manual labor ages you faster. And your MC doesn’t need to spread the message that helots deserve to be slaves due to their inferior nature; the Ecclesiasts have been doing that very effectively for the last few centuries.
If you start Harrowing every helot above 30, you’ll have a brief increase in blood phials – and then, unless you have some reliable external source of new slaves, you’ll have a collapsing helot population. You need the 30-somethings having kids to keep things stable.
Wulfy, the lack of grandparents is not all that odd – nobles have small families and often take a while to start breeding. Your father was an only (surviving) child, born when his parents were in their early 30s. He had you in his mid-30s, and you’re now 19. So he’s getting on, and his parents both passed away before any of the episodes that open the story.
Your mother came from a small House in the Lower Rim, which you’ve never visited; her father died young in an accident, and you remember your grandmother visiting two or three times in your childhood, before dying shortly before your mother did. You’ve never met your sole uncle, a naval captain who lives with his wife and children on the distant Coast and rarely visits his tiny patrimony in the Rim.
On religion, your definition so far would seem to exclude Theravada Buddhism, Confucianism, and arguably Taoism; belief in gods/“supernatural higher powers” is irrelevant in all three, as is afterlife. And you may be fine with that. It’s famously hard to come up with a definition that does comfortably include all the Abrahamic and non-Abrahamic “religions”; it’s perfectly respectable to say that not all societies have “religions” and that some things traditionally considered world religions should be considered philosophies or ideologies or whatever language you want to use.
Both in CoReb and in life, I’m interested in how rituals, symbols, and ideas related to Things of Ultimate Significance bind people together in a society, helping them make the necessary collective leap past meaninglessness – past that unanswerable “says who?” that threatens to reduce society to anomie or violence. When I see that going on, especially at national level, I’ll call it a religion (in the sociological/anthropological tradition I mentioned above).
Leader-worship can fit the bill – and of course Nazism was more than just a cult of personality, so the comparison to star-worshipping is not all that apt. But sure, some forms of fandom basically amount to a religious movement within the (small, sub-national) societies that take them with ultimate seriousness. Take the cult of Elvis: that’s a religion, no question about it. 