On the CO2 discussion, I was under the impression that CO2 is heavier than oxygen, you keep the CO2 on a low stream, and the oxygen is replaced by CO2 slowly, during this, the animal will get drowsy and fall asleep. When the animal is asleep, you turn the CO2 on high, and end it quickly while they are asleep.

And I can't see CO2 staying in high concentrations in a feeder for so long that it is harmful to the snake.