Hi! Here are some answers/suggestions to your questions:
Very hard to say what will be safety, stretch, and hopeless schools for you. I don't know what a GPA of 3.6 at UCB is worth. In which classes did you get As? Did you get As in calc III, linear algebra & diff equations, probability theory, and econometrics? Do you know your class rank/percentile? Additionally, it depends on how good your LORs will be.
Do you want to apply for fall 2005? If yes, you may get into problems because deadlines are soon. This may limit the number of universities you can apply to.
to 3) Pick LOR writers who think that you are a really good student. For example, ask a prof in who's class you were the best student. It might also be helpful to ask somebody who did his PhD at the school to which you want to go to.
I don't really understand what you mean with "how to approach them?". I just wrote an email to my prof saying that I want to apply for grad school and then asked "Do you feel comfortable to write a positive LOR for me?".
to 4) Yes, graduate schools weight GPAs from different Universities differently.
to 5) If you are worried about passing grad school, try to avoid those places famous for failing 50% of their incoming class. Second, take some additionally proof-based math classes.
I hope I could help you a bit.