Just a quick chemistry note: Aqueous CO2 is acidic, so putting CO2 into the bottle will likely alter the pH. Whether it would be enough to make a difference I don't know.
A long time has past since I was last on here, I have tried several ways to store the chemicals. The crown capped glass bottles were safe over the winter but exploded when the weather warmed, bleach, fix and dev everywhere. I lost around ten litres of each and the shed stinks of chemicals. I have resorted to PET fizzy drink bottles that I top to 1/2" from the top of the neck then squeeze out the remaining air, that leaves room for any expansion. I sold some of the bottles on FleaBay as an ECN2 kit so i can get wider feedback on the storage/usage life. So far all looks OK with using extended dev times over storage and usage following C41 Kit working solution guidelines. I'm working on a powder kit for ECN2 and C41, we see were that goes.