I have no clue as to the compatibility of your mod list, but generally speaking to your symptoms, the O2 not restoring and / or CO2 build-up and other strange nigglies come from "shelling out" to the Windows desktop, generally <Alt><Tab>, but <Ctrl><Tab> and the Windows key will all do similar. The SH series of games are from the single-threaded WinXP days (and previous), and 'expect' exclusive use of the computer. When you "shell out", the game loses its place and starts writing and using bad data. To fix that, Save the game, exit the game to Windows, take a deep breath, exhale slowly (that's what my doctor tells me...
), re-open the game, and then Load your last Save. Another thing to keep in mind about Saves is that the game doesn't like 'mixed' Saves, where if you were playing the game with a certain list of mods, you Save & exit, then change the mod list by activating more, or deactivating some, and now the game is different. The Save may run, but it is basically corrupt, as far as the new game set-up is concerned, and will cause issues as you describe above also...
