Shouldn't the man here be "vale" instead, since "I" is the subject and "man" is the object??
It should be vala, as a nominative.
Basic use: the grammatical subject of a sentence:
Āeksio yne ilīritas. — The Lord has smiled upon me.
Zaldrīzes buzdari iksos daor. — A dragon is not a slave.
[Where both Zaldrīzes and buzdari are nominative, although here it is difficult to tell because buzdari has the same form in the accusative. An example in the first or fourth declension would be clearer.]
This happens in some natural languages too.
And for the term nominal predicate:
A predicative nominal is a noun phrase, such as in George III is the king of England, the king of England being the predicative nominal. The subject and predicative nominal must be connected by a linking verb, also called a copula.
It's just the noun phrase which follows the copula/linking-verb to be.
the verb "to be" is intransitive, it doesn't have object of any type, being direct or inderect, that true in any language. that's why it doesn't have a passive voice.
In some languages this might be translated, "I am not your husband." Is Valyrian one of them?
Valzȳrys and ābrazȳrys are the Valyrian words for husband and wife, respectively. The etymology is most likely vala/ābra + zȳh- (his/her/its) + -tys/-rys (agent suffix). But it's possible that vala and ābra might be used to mean that as well.