Well, I'm not in Finance, but as you can see from my username, I'm from South America, maybe the same country. So, some concerns I had were similar to yours.
Some things to think about:
- A lot of universities in the world might be considered "unknown" here in the US, but still a lot of students are accepted into PhD programs. And at least a few professors may know a lot more than you expect to. I'm in Marketing, and I have been surprised sometimes when a professor shows knowledge about Brazilian brands, for example.
- Even if your university is unknown, universities often would be able to know more about them if they want to. For example, a top professor here at my department worked with a famous Brazilian professor in the past, and I know that they talked about me. I don't know if they talked to each other before accepting me or not, but at least it would be easy for them to check with a Brazilian about the reputation of my alma mater in Brazil.
- GPA is hard to convert, and they know it. Sometimes, schools may ask questions about the grading system of your school, or additional information. For example, your 7.8/10 would be equivalent to what? Top 10% of your class? My GPA is worse than yours, where I studied it's impossible to achieve a grade that would be close to a 4.0 GPA, not even the top student in the class was able to do that.
- I believe a high GMAT/GRE is essential in cases like this. At least, that was my strategy when I applied. It would hard to impress them with my GPA, or the university I came from. I focused on showing some research experience (and you have a lot more to show for that than I do) and killing on the GMAT score.
- There may be strong interest in South America in the Finance and Economics departments. I have taken classes with the guys from those departments, and generally speaking, the reaction is very positive. They know Brazil can be a powerhouse in Economics and Finance, given the complexities for those topics in Brazil. And I've met students from other South American countries too, like Peru and Chile.
- My LORs were also similar to yours. Since I did my masters in Brazil, it's only natural that the letters of recommendations would be from Brazilians too. I think it's just expected that your LORs are from professors in your country.
- Since you wrote you have an interest in corporate finance, I suggest you take a look into Accounting PhDs too. My background is in Corporate Finance, and I get the feeling that the guys from Accounting are closer to many topics of corporate finance than the guys from Finance.
I recommend you do a good job at finding the schools and programs that would be a good fit for you, and apply widely for a PhD, not MPhil. A master level does not seem to make sense, given your profile.
I'm not rich either, I had to save money for a long time in order to apply to many universities. Even for US applicants, it's very hard to make a list of only 10 programs that would be the best. For a foreigner, it's even harder.
About financial aid, at least in the US I don't think that would be really a big concern. PhD students get a financial aid package with the offer, if they are accepted, with tuition waiver, stipend, fellowships, etc.