joecollegedad, each year, 1000 people are chosen to be gates millennium scholars. test scores are not taken into account, however, the applicant must have a minimum unweighted gpa of 3.3. your other questions can be answered at this handy dandy site:
https://www.gmsp.org/GMSP%5FApp/
lyfe, to my knowledge, gates doesn't ask for your fafsa information unless you are selected as a finalist, which is in March. It is at that time that you submit you fafsa information to them. For the moment, don't sweat it. Just be sure to fill out your fafsa ASAP to meet your school deadlines, which should be coming up relatively soon, I'm guessing.
Hope this helps. anyone, feel free to correct faulty info.