I have complete family history from ASA to present. ASA was the one who changed the name from 'a' to 'o' in 1838 when he arrived in missouri. The change was because he was getting to much mail of unrelated Calverts and there were many in MO. James Asa, is buried in Selby County - if my memory serves me correctly. Right now I'm looking at Robert Calvert of Charles County MD and Charity Gray as somehow connected to ASA. ASA's oldest son, who shared deeded property with in MO was named John ROBERT. Fairfax was in family records as his mother, but it also states ASA had a step-mother. Your connection is listed in our records. I also descend from Washington Lanty through John Waddy and have WL's cane. ASA also had an older brother named Lanty Calvert. Lanty lists ASA was heir in his will.
My biggest problem is connecting FAIRFAX. My DNA shows a connection with WEST/FAIRFAX - probably the Henrietta Fairfax line.
Hope this helps. Please feel free to contact me anytime - cousin. I live in Cody Wyoming.
William Waddy Colvert