Re: Donald Dubh abt. 1400 to: Somerled Isles
I can't say if it's proven or not, but being on file at the Library of Congress (or any other library) doesn't necessarily constitute proof, in and of itself. You'd want to compare it with other good sources to determine how valid the information is.
In comparing to what you have, other than a couple of dates that don't match, it is essentially the same up to our common ancestor Angus Og MacDonald. After that I couldn't say with any certainty. I haven't followed your line as far as you have--only as far as "Alexander (Alasdair Carrach)"(the Gaelic spelling one of my sources provided).I descend from Mary MacDonald, John's (Ian's) sister.
Recently, I've been working with another source that covers at least part of this line--"The Complete Peerage" by George Edward Cokayne. So I've been busy inputting information from those volumes into my database as well. You might want to check for yourself to see how much of your line might be mentioned in that work. I found part of this line in volume VII, p. 76 and in volume VIII p. 143. It's a start anyway.
As far as tracing the line backwards, yes, I found Conn "of the hundred Battles" is a direct ancestor to Gilledomnan, Gillebride, and Somerled. And for a great deal of this line, in addition to other sources, I also referred to "The Annals of the Four Masters," which is available in its entirety online if you're interested. Much of the information in that source is considered legendary, but it's also the best information available for the time period covered. I just entered a note at the appropriate person stating that: "earlier than this person the line is considered legendary"
At any rate, thanks for posting the information. Did John Hunt happen to mention what sourced he might have used by any chance?