Generally speaking, I find availability RIC-MIA very hard to come by when flying AA nonstop. That is likely why you are seeing a routing RIC-ORD-MIA-EZE.

However, I am seeing availability on the AA daytime flight from MIA to EZE on March 7/8 returning March 12 again on AA daytime flight. I am also seeing availability in business/first class for flights that work as connecting times from DCA (though not IAD/RIC and nothing in coach). They do mean for some long days, though - like departing DCA at 6am and returning at midnight.

If the flight times work for you, I'd use the 50K AA miles for one person's one-way DCA-MIA-EZE, and then 50K pp per direction of travel MIA-EZE for a total of 150K Avios. I'd then wait to see if availability opens up in coach class on the desired connecting segments DCA-MIA or simply pay cash. The remaining three one-ways should cost you roughly $350-400 and save you Avios for future use.

To avoid these really long days, consider flying the DCA-MIA segment the night before with an overnight layover in Miami and pay cash for the segment MIA-DCA to get better flight times on the way home.