Yes, and they sailed off to conquer Aman
Many of them had already settled in Middle-earth as well.
The ones who were faithful were the families of Elendil and his sons. Those are the ones who left in the ships. There were probably some servants and such, but by the time of Lord of the Rings, intermarrying would have given most, if not all of the Dunedain the blood of Elros.
This just isn't true. The house of the Stewards of Gondor, for example, which included Denethor and his sons Boromir and Faramir, was not descended from Elros, although they were of noble blood. Nevertheless, they enjoyed long lives.
I'm not confusing anything.
You certainly are. You're claiming that the longevity of the Dunedain is attributable to non-human ancestry, ignoring that the majority of the Dunedain who lived in both the Second and Third Ages were not descended from Elros, and yet had longer lives than "lesser men".
The ones who settled the mainland were also Black Numenoreans, and not Dunedain. Only the faithful became Dunedain, and the faithful were the families of Elendil and his sons.
I see this has devolved into a semantics debate. Perhaps it was from the beginning. I had assumed that by
Dunedain you had meant the race of people to which Aragorn belonged. They were the people of Numenor and included any people that had its origin on that island, including the Black Numenoreans, although they became mingled with the Haradwaith they lived among, just as the Dunedain of Gondor intermarried with other men of that region. You seem, however, to be attempting to redefine
Dunedain to mean only descendants of Elros through Elendil. I would hardly call that a race. By the end of the Third Age, I doubt there were any members of that group left besides Aragorn himself. My intent here wasn't to debate the meaning of the word
Dunedain with you, however, and I do not intend to continue to do so.