Pam, I'm glad to see that you posted again. I would like to comment on a few things you brought up in your post.
Pam, it seems I gave the mistaken immpression that I believed some of my Dalton ancestors were Melungeons. To the best of my knowledge, none of them were ever called a Melungeon. However, Pittsylvania Co. Va where my ggggrandparents come from, was IMHO, the home of a crypto-Jewish community. Some Melungeon families sojoured a while in Pittsylvania untill they moved west to Wise Co., Va and Hancock Co., Tn.
Your connection of the Mustains with mining is interesting. My gggrandfather, Avery Dalton, ran and owned a coal mine. He was thefirst person in Peoria/Knox/Fulton Counties area to mine coal commercially.Both Jews and Moors were reknown for their skills in finding, mining, and processing precious minerals and metals. I wonder if some of his Mustain kin taught him anything about mining.
You seem to think my ggggrandma was named after the Seludy River. I can see that is a possiblity. But were did the name come from? I believe, based on the evidence of naming patterns in my family, it is a variation of the Spanish name Saludah. Several of Seludy's grandkids by Avery had Spanish names. Alameda and Seludy were two daughters with Spanish names. Also, Avery's eldest son Cicero married a lady named Clarinda Delictia Dixon. The first name is Spanish, the second one is Portugese. Dixon is Scotish, but recent DNA testing shows that some branches of this 'Scottish' family has Spanish/Portugese/Jewish roots. DNA testing on yours truly shows simular results, with ancestory from China too! (I have almond eyes and buck teeth too.)
You mentioed the Canary Islands. I have markers in my DNA results for the Canaries. I also have markers for Africa. Since the DNA Fingerprint Test showed no Sub-Saharian DNA, it would probably be North African, probably Moor or Tuareg.
I still believe the name Mustain is probably the same as the Arabic name Mustain. You seem to believe it comes from Gaelic. We both believe in a sea going connection. I have DNA from the Middle East, the Far East, the West Indies, and even Indonesia. Somebody was doing some sailing back then!
Has any Almustaine male's Y-DNA been tested? That would help your research quite a bit.