You got accepted at a DO school. You have a chance to be a doctor. You still have a chance at the MD school between now and the day of matriculation. SGU and Ross accepted you because you are above their minimal requirements on stats and you have the ability to get federal loans.
Your numbers are significantly low for most MD schools. While you would be considered an URM and that improves your chances, it still won't change things alot for you.
So what should you do? I would go with the DO acceptance and run. Yes, you have to learn OMM. Yes, they say they look at patients holistically and MDs don't. But really, it just means you learn OMM and have to be tested on that. When you finish school you can blow that off if you want and never worry about it again. DO is not a disreputable path and is, in fact, a legitimate path to practicing medicine. Years ago there was more of a stigma against DOs than today. But years ago the Caribbean schools were also a reasonable path to medicine for nontraditional students as well. Now? Caribbean students fight uphill battles to get residency programs. You have to make it through your schooling and pass certain exams and milestones just to be able to take some of your Step exams. Then you can't just pass those exams, you have to do above average. Then you have to get through your clinical rotations that could be scattered throughout the country. Once you do that, you apply to the match for a residency slot. Maybe you'll get in that first time. Maybe you won't. I've seen many stories from Caribbean students who apply to 150-200 programs and get maybe 10-15 interviews. Compare that to a DO student who would apply to less than half that and get a much higher number of interviews. In fact, by the time you would be graduating, the DO and MD program merger should be underway if not finished, so you will be accredited by the same group as MD residencies. You will have a far greater chance of matching.
Now let's also be realistic about your chances based on the info you posted. Your grades are below average for medical students and your MCAT is below average. If you go to the Caribbean you will have less help and far greater chances of flunking out. Of course, you may say that'll never happen to you. You'll be the one to get all A's and be in the top of your class. Maybe you will, but your past history does not suggest that. Compare that to a DO school. They have an investment in you and a desire to see you graduate. You will have more support and resources if you struggle.
You have people like VegasSurgeon who claims that Caribbean MDs are more desired than DOs. I find that attitude is mostly seen only in premeds and perhaps some in the older generations. Nowadays as a DO you have a chance at most anything you want. Yes, things like neurosurgery, ophthalmology, and derm might be harder, but those are hard for MD students as well and they are certainly very difficult for Caribbean students.
I would recommend taking a good hard look at things before you turn down a DO acceptance. Any future applications to MD schools will likely ask if you have been accepted to medical schools in the past and you may be hurt for turning down a DO acceptance. You have your chance now to be a doctor. How bad do you want it?