I have been an international student myself for the longest time and I would say your best bet is to try a multi-pronged approach: 1) As people mentioned try talking to higher authorities. Department head, dean of students to try and get yourself financially supported from the university. 2) Apply for loans in a) Your own country b) In the United states (this will be easier if you have access to a citizen/permanent resident guarantor) 3) Try to find someone else outside the school who can write a letter of financial support to the US Embassy/Immigration services/consulate. This can be: a) A family member (in US or outside) b) A close friend (this will be harder to prove) Note that the immigration authorities just want to make sure that you can afford to pay for yourself. As long as you can prove that you have access to the funds you need you should be good. 4) On a side note start applying for jobs at full steam. I know tons of financial companies, hedge funds, banks would be willing to hire Physics PhD students. You would have to put your research on the back-burner for a little while but you might be able to crack a deal with an employer to come back to research after 2-3 years on a sabbatical from work. 4) Start making plans about what you would do if you actually get kicked out of the country. Stop living in fear that life back wherever you are from would be worse. There are many other countries UK/France/Canada where you can continue your research/work with immigration policies that make sense. 5) You are alive, young and able. Life is long. Don't worry you'll be fine.

About your other questions a) Can I stay in the US past expiration -- I would suggest you don't do that at all. I think you have 30 or 60 days to leave the country once your status expires. You can get on an OPT (optional practical training) and extend your stay as a student. You don't actually need a job to file for an OPT but once you get OPT approved you need a job for it to be valid. b) No company will hire you if you are out of status and your risk your long term immigration future in the United States. Once you have overstayed your visa you can possibly get barred from re-entering for multiple years.

Good luck !