Will God forgive one who is afflicted with secretly viewing pornography for arousal and to fulfill one's desires permissibly, while feeling extreme guilt and seeking forgiveness, and not committing major sins?

What you are doing is forbidden (haram), and you must immediately repent from it. Persistence in sin transforms a minor sin into a major one. Beware of Allah's wrath and His plotting, and hasten to sincere repentance. Read the book "Ad-Daa' wa Ad-Dawaa'" (The Disease and the Cure) by Ibn Al-Qayyim. Increase in good deeds that expiate sins, for one who repents from a sin is like one who has no sin. If you remain persistent, then you are under Allah's will, and there is fear for you of His displeasure and punishment.