Error 1: Every «huwa» is a separating pronoun. Correction: the form may itself serve as the nominal subject; examine syntax.
Error 2: «Zayd huwa al-qāʾim» means that standing is Zayd’s only property. Correction: the discussed restriction attributes the standing to Zayd; it does not erase his other attributes.
Error 3: Only a separating pronoun can express restriction. Correction: «iyyāka naʿbudu» illustrates another means.
Error 4: The pronoun offers no structural benefit. Correction: it can help mark the distinction between a predicate and a modifier.