The time beforehand is not critical. I have an 8am bris and that's about it.
Probably will Uber.
T1.
In that case, as much as I hate MIA airport and despise AA, I would probably be inclined to take AA, though I'd probably check status and options on the day of flight. The bottom line is that there's no way of knowing what will end up being a better option, and the AA is a short flight.
I will qualify this by saying that I once connected at DCA, and it was a breeze. I can't recall if I ever connected at IAD, if that connection is supposed to be easy based on gate assignments (though they could definitely change) and conditions at IAD, I might opt for that.