Most medical schools do not accept online coursework for pre-reqs classes. They especially will not accept online credits for courses that have a lab component (bio, gen chem, ochem, physics). They did during covid, but since all universities have returned t in-person instruction, med schools have returned to their former policies of limiting/refusing online credits. There are a few exceptions allowed for people who do not have access to in-person classes like US active duty military personnel.
For MD/PhD, there is a very strong expectation for significant in-person laboratory experience. You will need a very strong LOR from your research PI to support the PhD part of the application. MSTP applicants must be accepted independently by both the medical school AND the graduate department of their chosen research area. If not accepted by both, you are rejected,
A second bachelor’s degree is unnecessary for applying to medical school. While US medical schools do not accept degrees earned outside the US and Canada as fulfilling admission requirements, international grads with foreign degrees can be accepted as long as they complete 30-90 credit hours (varies by specific school) of US coursework that includes all the pre-reqs for med school.
If you are interested in a USMD, a post bacc for career changers would be your fastest and least expensive option.
Post baccs are not set up to for MD/PhD students. You would need to lean on your foreign degree and research for the PhD part of the application
MSTP program are restricted to US citizens/USPR since they are funded by federal monies. There are non-MSTP MD/PhD programs but not all of them are funded programs. (IOW, you would be expected to pay for your own medical education, though it’s likely you could get funding for a PhD from a research supervisor/thesis advisor)
I am unclear as to WHY you need a MD/PhD for your career goals. Those who seek an MD or MD/PhD must be interested in clinical medicine. They are patient-centered in their outlook. Even, MD/PhDs see patients all through their career. MD/PhD career trajectories include a split of duties between clinical duties and research.
I don’t see anywhere in your discussion an interest in seeing patients.
You also need to understand that gaining an acceptance to US med school requires more than just completing the expected coursework. Med school admissions also expect applicants to demonstrate they have all the necessary Premed Competencies for Entering Medical Students. The list includes interpersonal and professional competencies along with science and critical thinking competencies. For example, demonstrating the Service Orientation typically requires a significant amount of volunteer hours working with disparaged and disadvantaged groups in the US.
Besides academics, med school admission informally requires having enough experience within the US healthcare system to demonstrate an understanding of how the system works and what the physician lifestyle is like. A few hundred hours of clinical exposure in the US healthcare system is a soft requirement for med school admission–even for MD/PhD applicants. 50-100 hours of shadowing US physicians is another soft requirement. Shadowing must include several different specialties including at least one primary care physician. (Primary care includes family medicine, general internal medicine, geriatrics and pediatrics.)
Acceptance rates to US med school are quite low. Individual med schools frequently have acceptances rates in the single digits. Individual MSTP acceptance rates are typically under 5%, often in the 1-3% range…
If you really want to create a successfully application for MSTP or Md/PhD programs, you need to have US community service and US clinical experiences. If you are currently living overseas, you will need to postpone your application until you are able to move to the US and obtain the necessary experiences to support an med school application.