It sounds like you are a pretty regular smoker so dillution maybe a bit risky for you. You can still try but make sure you pickup some cheap thc test strips to check yourself. I get them for about $1.25 each off ebay.
Don't think taking th Qcarbo will really hurt but I doubt that it will help much.
STarting the creatine a week before the UA should be plenty of time for it to metacolize and make its way though the urine.
I always recommend subbing with synthetic urine for anyone other than a once or twice a week toker. Its just not worth the risk and stress trying to get clean.