Odd thought… Any chem majors out there? Or maybe a geology buff I what I am thinking of?

I’ve been reading earth history lately and have a question.

If we have all that methane trapped in ice and permafrost… And methane reacts with oxygen to turn onto H2O and CO2… How bad would losing all that methane to the air be for oxygen levels in our atmosphere?

There was some theory about how the Earth might have two stable points for oxygenation - 20% (current), and like 0.02% (pre-photosnthesys / the oxygen catastrophe). Could we all be worrying about global warming in vain when really we’re all going to choke to death from lack of oxygen? Or is there just not near enough methane in that ice/permafrost/etc to harm the O2 levels?