I'm almost convinced

But have I convinced anyone else?
Some additional circumstantial evidence for the theory of the the two James families, that of James and Margaret (MABON) RICHARDSON, and that of James & Christian (OUTERSON) RICHARDSON being one and the same James:
-  George (mother MABON) also emigrated to the States and is to be found in Omro, Winnebago, Wisconsin in 1860 three census pages before his presumed step-brother Robert who has his mother Christian (OUTERSON) living with him.
- George 's wife is Margaret MELDRUM
- David, George's assumed step brother names his daughter Ella Meldrum RICHARDSON
- a snippet view of "New Brunswick Lineages" on google books brought to my attention by John shows James as 1770 (Edinburgh) -1850 (Lower Canada) - which age makes it highly likely that he remarried (Christian was born around 1796)
So, just maybe John's Adam, born 1835 New York, belongs to James and Christian? This is only 3 years after their last known Scottish son was born.
All pure speculation of course, but even though there isn't, yet, a proven dna signature for James' line(s), we do still have a Bermuda, and a New York connection.

Love to hear from any direct male line RICHARDSON descendants of the above families who might like to explore this further.