Even if the kids don't know about the drug use, they know something is very very wrong in that household. You're kidding yourself if you think different.
What is your bottom? I don't know. For some the bottom comes when they can no longer stand the pain of living and commit suicide. I was close to that at one point. Codependency can and does kill. For some, they die at the hands of their abuser. Codependency can and does kill.
For some, they just exist like that till they are old and bitter, and figure it's too late by then. Often they get to see the pattern of addiction repeated in their children as they grow up.