At that rate, will I be clean enough at some point, that a week or two of not smoking at all would not show up on a test?
Theres no telling. Each persons body is different and there are too many variables to take into consideration. Only periodic testing with a THC test kit can give you that answer.
I know the best way is just to stop smoking completely.....but who whats to do that.....?

Or should I keep smoking like a freight train, and just rely on the QF ? (never used QF, so I'm still a little nervous about pulling that off).....
Thats a decision that you would have to make. If you want secure a job yet retain your current lifestyle, then subbing with the synthetic or a clean persons sample would be the way to go.