It does you no real favors by med schools graduating a year early (with exceptions, obviously, but you don't appear to be one).
1. You don't have to address that, they'll see and as long as you have the necessary courses/credit requirements it won't matter.
2. The higher the gpa, the better. If your spring grades give you a significant boost, then wait to include them. (I would)
4. It's very dependent on the schools you're applying to. Look it up on their school websites or msar. For example, Jefferson requires either the committee letter OR four letters (bio,chem,physics, humanities) if you don't have one. Be very careful regarding this because that would be a very bad reason to not get into med school because you didn't do your research on this.
5. In general, you don't include what you did in high school on your application. It may be placed in your PS if it was that meaningful and helped you make your overall decision to pursue medicine. However, without any active clinical experience throughout undergrad (you appear to have ZERO volunteering, actually), your application may very well be dead in the water. Many adcoms here have stated it is 100% necessary along with shadowing. They like nonclinical volunteering to show your altruistic side.
6. That won't matter at all. Something like 2/3s of all CA applicants are forced to leave CA to attend med school every year. Yes, you may have a compelling reason, but so does everyone else.