Regarding farming, I believe it can’t be balanced by just changing some numbers. The math doesn’t work out.
Under the current system, crops grow exponentially. That’s in opposition to a progressive learning curve, where things start easier and get harder over time. No matter how you adjust that exponential curve, it’s going to be too hard for players at the low end of the curve or too easy for players at the high end of the curve. You'll never find values for vegetables per stew or yield per plant that accommodate both ends of the spectrum.
Now, you can dismiss the problem by concluding that you shouldn't bother fixing it because food isn't a big part of the game, or that experienced players are just too good to be worth balancing the game for them. But I would point out that other parts of the game do have a balanced progression curve, namely the game stage and heat systems. These systems already accommodate all kinds of players well, from the 10 hour player to the 1,000 hour player, by scaling the zombie threat based on how successful you’ve been.
Farming could draw inspiration from these systems to have its own progression curve. What's critical is that there be some mechanism whereby the more plants on your farm, the more challenge you're given. This could take many forms. I would favor a system directly analogous to the above, where rabbits and deer attack your crops, and their number and frequency is related to the number of plants making 'heat' in a chunk.
Most of the pieces for that, both art and code, you already have. And that's good in part because it means there's gameplay there you already have, too. I.e. there would already be different ways to counter animals attacking your crops. Whereas if crops randomly die for no reason, what does the player do about these random failures? Buy a perk? Engage in some new farm-specific gameplay you have to code? Nah. Just lean on the tower defense, traps, gunplay etc. you already have.
But again, I'm not attached to animals eating crops in particular. I'm just looking for some way that a bigger farm is harder than a smaller farm.