1.
http://officialguide.lsac.org/UGPASe...spx?SidString= This is a good way to figure out your approximate chances at schools. If you don't get into a school with a national reputation, go where you want to live and where it's the cheapest cost after scholarships.
2. Personal Statement is important if you are borderline. How you describe your PS is what most people write and probably won't hurt you.
3. Letters are less important than the PS, still might matter if you are borderline.
4. Yeah, go ahead and apply. The school won't consider you until your lsac package is complete i.e. your letters are in.
The bottom line is your LSAT and GPA will (probably) determine where you get in unless you are an under-represented minority. Also check out this forum and repost this IMO.
http://www.top-law-schools.com/