Gardening in the face of pests - what's the effect of covering plants?

I gave up gardening a few years back because the pests won. Earwigs, snails, slugs and rabbits ganged up on me.

I’m trying it again in a limited version. I have just a few plants. I’ve taken to covering them with glass bottles or the like at night. I think there’s been some reduction in damage.

I was wondering about the effect this could have on the plants’ growth. Specifically, I’m trapping the oxygen the plants give off and diluting the carbon dioxide. Obviously, that can’t be good for the plants, but I don’t have any sense of the VOLUME of oxygen created. In one day, will the CO2 change significantly under my bell jars?

For that matter, could I do something to increase the CO2 in the captured atmosphere and speed up the growth?