It seems to me, from your post, that you would be an international student (someone who needs to obtain an F-1 visa in order to study in the US).
That makes you very diverse. But there are no official quotas for women or minorities.
You are right, the higher ranked the school, the easier it is to get a job with a prestigous law firm. But you would most likely need above a 155 to get into one of those firms (Top 20 at best/worst). On the other hand, they may cut you some slack because English is not your first language. But they may not. That is a question for the schools themselves.
Work experience is a bonus, as is a graduate degree, but neither makes you a guaranteed admit anywhere.
I do not know where to find figures regarding private sector self-employment, but know this:
if you need a visa to study in the US, you will need a visa to work here too, which means that you will need an employer to sponsor you, which means that working on your own in the US is out--unless, of course, you can be come a Legal Permanent Resident (green card holder) on some other grounds, such as marriage.