I don’t use Co2 so I’m not positive, if I remember correctly you need quite a bit of Co2 for it to make a difference.
As far as oxygen in the soil I don’t think you can have too much.
To tag someone in a journal put an @ symbol next to the persons name I.E. @irma1010
co2 is like lights. Lots of opinions. It definitely works, but for the home-grower to use it effectively is another question.