Does it need the pronoun "o"?
Yes. When you have pe you also need the pronoun.
Why the two last ones do not have le & pe? Accusative pronouns seem to be used only for people at least, but what about the last example?
The accusative pronoun refers to a particular person or persons, but the last example above -- "Eu iubesc femeile" means "I love women" in general.
Te iubesc - i love you