It is a mystery to me why the GRE is a thing. It tests basic but general knowledge. If I were evaluating a potential grad entrant, I don't think I could glean anything from a good score, although I guess I may be able to glean something from a bad score. GRE notwithstanding, I think public health is only going to be a growth area. You should find a place that is in need of grad students, then you can probably get a research or teaching job and scrape by on a stipend but at least no debt. It will be well worth the effort of looking even if you come up empty.
Public health won't be a growth area without massive changes to our healthcare system. Right now Capitalism benefits short-term profit and reactionary responses to disease rather than proactive prevention because there is more more money in charging someone to fix their a leak 100 times just enough so that it can break again, than seeking a long-term solution just as there's more money in giving out antibiotics and charging instead of waiting to see if they're at all necessary gets more money even if from a public health standpoint that's horrendous. As soon as they don't have to be spending a lot on public health, they'll cut it. I can hear it already, "we just had a pandemic what are the odds we have another one soon? Everyone is prepared for it this time around" and bullshit like that. Public health is chronically underfunded and this pandemic exposed that beautifully but I doubt anything will change in the long-run. In the long-run, everyone is dead, so why invest in it?
It's not always about investment. The question is rather, who benefits from advances in public health? The answer is insurers. The biggest insurer in the country by far is the federal government. They're going to want to learn and apply lessons for many years to come from this catastrophe. I suspect that NIH will ramp up public health funding, and other large insurers might spend some money on it too. I would go for the PhD of I were you. Don't stop at an MPH. You're smart enough, dedicated enough, so why not just go the whole way?
There's a real chance I go for a PhD down the line, but I want more experience as those tend to be hyper-specialized. I'd be looking at infectious disease and infection prevention, but specialization with that. Probably novel/necglected or something like that, but that's a future me problem. Taking my life one week at a time at this point.