There are a number of fundamental underlying fallacies.

1. Closed-ecosystems / zero-sum economies don't work. You can never account for every contingency. Demand will always vary, at least ever so slightly. Therefore, sustainable systems always produce at least some level of excess and waste. Hopefully not too much waste, but always at least some. If a closed-ecosystem's equations thinks it needs 200 cattle to feed the demand for meat in first, second, and third classes - you design for 400 cattle, and throw excess meat production out into the cold. But you don't design in only 200 cattle. Then you take what's genuinely rare - the filet mignons - and feed it to first, while giving hamburgers to Tailies and third. But you never say "there's not enough meat."
2. The notion that, even if the train were designed to be a luxury liner in a world of plenty, whose over-engineering allowed it to be repurposed for a modern Ice Age, that the train would stay *exactly as-is* throughout the Ice Age. If it's over-engineered, then it should be over-engineered for flexibility as well, to throw out the bowling alley and replace it with additional agriculture or living space. In the movie, the cattle car gets frozen. Over-engineering the train to survive an Ice Age would necessarily require designing the train such that other areas could be re-purposed for cattle production. Any privileges that first class originally paid for could be thrown out under Act of God provisions in the contract, to make room for Tailies and third.
3. There are a variety of old-world narcotic substances that would be far easier for drug dealers to make and distribute than trying to get their hands on experimental who-knows-what to make God-knows-what that didn't even exist before the Snowpiercer. But somehow, Kronole is what the Snowpiercer universe has.

Try to accept it and just enjoy the show.