But if you're saying miracles can't be tested or repeated, then it's not scientific, so I'd say you really can't know those things for sure

I understand what you're saying. That's called empiricism, which says all knowledge must be scientifically testable and observable through the five senses. Empiricism was a popular idea during the 18th century, but by the 19th century, we realized that it's too extreme to say that if something cannot be tested or repeated, then we cannot have knowledge about that. Because by that standard of "scientific" evidence, any one time events, like any event in history or even the Big Bang, would be unknowable, because you can't repeat it. But I think most people would agree that it would be unreasonable to say we can't know some history. It's true that any historical event, because it's in the past, does not yield to the five senses or a test tube. But we can still have some historical knowledge, can't we? For example, the knowledge that Abraham Lincoln was assassinated, knowledge about some genocide that occurred knowledge is not really empirical anymore, because you can't test for it in a lab. All we have is historical records. But I think we can know those things with a reasonable amount of certainty.

So I think we can be reasonable and be open to the historical evidence.