I have read several advertisements and testimonials about interview coaching for the FBI Phase II Oral Interview. Given your situation it might be worth looking into, rather than simply retrying it a second time on your own. Good luck. I wasn't selected to move on to Phase II after I passed the written test - if you would, I am interested in what your back ground was to even get selected, let alone fast tracked. Good luck to you!!
As a nation we adhere to the maxim: "The object is not to die for one's country, it's to make the other poor son of a [gun] die for his." - Gen. Patton