On January 10, 2015 I ate 1/3 of a pot brownie. One week later on Jan. 17, I took two hits of pot from a bong. In the past 90 days (even later than that), that is all that I have done. I found out I have to take a hair test for an upcoming job. I am still unsure of when I will have to take the test but it will probably be in a few weeks or a month. Will I pass this test or should I waste money on a practice test to be sure? Any thoughts?

How much is peace of mind worth? It will give you a good idea of where you stand. From what I have read and what I understand of the test in question you shouldn't have to worry about anything. The test looks for habitual use not occasional use. Three uses isn't going to cause you to fail. If you had smoked up every night in the last 3 months that might be a different story, but if what you've posted is true then you should be fine.

A hair drug test is meant to show consistent use over time. A 1.5 inch sample, cut at the scalp line, will go back 90 days. Since you didn't ingest much THC my best guess is that you will be negative on a hair drug test.

You SHOULD pass easily from what you have written.

I just found out that for the 2 bong hits, there was kief sprinkled on the pot.. Does this change anything? Thanks for your answers!

No difference.