None of the three women before him believe in his words. (or "believed," for past tense) Add an /s/ if the subject is singular; don't add an /s/ if the subject is plural. The subject and verb must agree - if a subject is plural, the verb must also be plural, and vice versa. In the present tense, nouns and verbs form plurals in opposite ways: nouns add an /s/ to the singular form; verbs remove the /s/ from the singular form. Of course, in this case, the plural form of "woman" is "women." You also have indefinite pronouns that are both singular and plural, which I won't expand on.
It really depends on which translator you work for. Personally, my editor and a few others of translators I know are pretty well-compensated because we appreciate the work they do and their talents.
^This Professional editors get paid from 1 to 5 cents per word (depending on the type of edit they do) Also, form the examples you gave, that would be copy editing, and those editors (pro ones) know the rules of grammar like the palm of their hand.