Well, I'm basically done with my Hell playthrough, the remaining stuff just needs to wait for a few more lawachurls to spawn then I can steamroll everything.
For anyone struggling with population, the BY FAR easiest way to manage it is to just never fully upgrade your settlements. You'll regularly get renovation upgrade options that require lots of hilichurls. If you renovate to max-1, these are like 400+ hilichurls at a time. If you have 3 colonies at once (springvale, and two others on the upper left side) you can basically infinitely ensure you don't get into overpopulation territory. As far as I can tell you can infinitely add upgrades, so long as you don't hit the "renovate" button to finalize it. By finalizing the settlement you get more, and more varied, slaves, but in my opinion the population control is way more valuable.
I just checked every turn whether I had the option to sacrifice hilichurls, did it if the option was there, and am sitting at 99999 food right now.
Also if you're not using abyss branches you're making your life way harder for no reason. They're crazy useful. Take a forward position and then just teleport a full stack of powerful dudes into it. By mid-game I could make branches every turn so running out was never a concern.
I never used any of the girls in my armies. I have no idea if they're supposed to be good or not, I just never found a reason to do so. Not sure if that's just me being lazy or if the game should try to encourage it more. But the irreversibility of corruption + limited nature of brainwashing masks, and the opportunity cost of not having them breeding, made me never want to bother using them. Just throwing that out there.