I had between 3 and 4 drinks (liquor) on Friday within a 3-4 hour period, stopping around midnight or 1am. I took an ETG test the following Tuesday at 2:30pm. I used and online BAC calculator to determine that my BAC would be 0.00 after approximately 6 hours. Thus, I had been free of alcohol for roughly 80 hours prior to my test. I am a male, early 20's, 6'1", 150lbs, moderately athletic, with a high metabolism (Read: skinny). Can someone weigh in on the probability that my test will come back positive at the 100ng and 500ng cut off levels?

I would GREATLY appreciate your input.

Bit late to worry about it now really.
What happens if you FAIL ?

You should be OK at 80+ hrs.

Don't drink and you don't have to worry. Its just a matter of time before you fail one if you don't.