Are viewing pornography and masturbating because of it considered zina and betrayal?

You must advise your husband and remind him of the impermissibility of what he is doing and the danger of sins. Give him the book "Al-Jawab Al-Kafi" by Ibn Al-Qayyim. As for masturbation, it is forbidden, and its sin is greater for a married person who is able to keep himself chaste through lawful means. However, committing it is not considered zina (fornication/adultery) that necessitates the hadd punishment.