Deus is translating "elohim" which is plural. Note the -im suffix for plurals. Modern Arabic has a similar suffix.

Elohim is frequently translated into a singular form to support monotheism. But it's definitely not a grammatical construct, like English's royal we.

Now, plural gods in Genesis 1 do not imply that the Genesis 1 creation only covered Jews. I don't understand that part.

In any case, I was really asking what modern biblical literalists say to resolve this "Seth picking up a wife in Nod" issue. I'm sure they have some kind of story or explanation, and frequently I find those kind of hilarious.