It's also my understanding that folic acid is excreted if you get more than your body can use -- it's water-soluble -- and the only thing I'm aware of that's related to high doses of folic acid is that it can mask pernicious anemia, which would have shown up in your blood labs and which pretty much only happens to the very elderly and to extremely strict vegetarians who don't take a multivitamin, so your prenatal would cover that.
Asking your doc about the baby aspirin is your best bet. I think there are some studies suggesting a benefit from baby aspirin for a subset of women wrt conception, but I'm not sure (and I'm not sure if you're in that subset, but your doc would be.)
And don't forget, correlation isn't causation. :-) Touching the fuselage of a plane every time you get in one doesn't cause it not to crash, even if every time you touch the fuselage before you fly, you land safely. It's hard to keep our brains from running away with causes, but I don't think there's any good evidence to suggest a link between miscarriage and folic acid.