To get a better idea of your potential for passing you should also include your smoking history (as in how much per day etc) and how much you excersize. You have a lot going for you though. A low body fat % and i'm assuming a high metabolism. Yeah you will get conflicting results on how long it stays in your system because it is very very different for everyone. Typically the time window is between 3-30 days depending on how much you smoke with rare cases of people testing dirty after 60+ days.

Since you didn't mention actually having a drug test on a set date I would tell you to just wait for at least two weeks just to make sure you will pass. You may be testing clean already but if you do not want to wait the two weeks I would follow the dillution sticky at the top of this page. Also, drinking water days/weeks ahead of time does not speed up the process at all. It really does more harm than good if you drink an absurd amount of fluid because it just isn't healthy. Just drink enough water to stay hydrated like a normal person would, the water loading really comes into play the day of the test.