I have not read the dissertation, but in the passage you quoted every single example fits with my understanding of what Maimonides is saying - they all come from verbs. That is, except for betulim, but that is because betulim always denotes two things, that she is physically a virgin, and that...
Maimonides writes in the Guide (1:2) that Elohim is a homonym that denotes God, angels, judges, and the rulers of countries.
As to why the plural form is used when signifying God: in the passage I quoted Maimonides suddenly digresses to explain that panim, the Hebrew equivalent of face, is...