The answer is very often it depends.
1). What kind of research are you doing for your professor? How good is your professor? Is it relevant to what you want to do as a PhD ?
2). It depends. Are you ready for gradschool? What are doing these 2,3 years?
3). Luck is an important factor. Is there faculty available for your topic? How good are the other applicants that year? Don't underestimate the GRE, especially if you are not a native speaker. Also, LORs are very important. Many foreigners don't know how to write them (and even some Americans don't know how to write them). Even if they are very positive about you, they may not be great writers.
4). Depends on what you want to study. It won't help much if what you are stuying now is irrelevant to what you want to study as a PhD.
5. Yes! Getting a PhD is not about getting a title from a top 10 program. You should be passionate about your research and apply to schools have a great reputation in your subfield. Don't go to the websites of sociology programmes and check whether they have faculty that you like. It is the wrong approach! Only apply if you have read a substantial amount of work by scholars in your subfield and then check whether they are at universities with a PhD program (what their graduate students think of them, where their graduate students ended up, if they have funding, what the school offers etc).