1) One generally meets docs while volunteering and asks them. You could also ask your personal physician back home, the premed advising office at your school, or cold call local docs' offices and ask if they would take you.
2) What you're doing is clinical experience. If the hospital won't let you work more closely with patients, try a nursing home, clinic, or hospice. You may need to do this anyway to have better contact with physicians you can ask to shadow.
3) AMCAS will recalculate your GPA according to their own rules, regardless of your current school's policy. So your AMCAS GPA would include both grades.
4) The difficulty of your currnt school is more likely to be regarded by the highly-selective med schools. There are many that don't mind you taking community college classwork (though there is the risk that such classes won't be sufficiently rigorous). I think you'll be fine taking classes at any four-year college. Go where you can get the highest GPA.