What is the ruling on marrying a suitor who possesses religiosity, good morals, and knowledge, but watches immoral content on his phone, claiming that it is a way to avoid a greater sin, and links his repentance to marriage, believing it to be the solution?

The question indicates the inquirer's awareness of the pornography problem and that marriage might not necessarily solve it. No one can make the decision for the person facing the problem; the decision remains the inquirer's responsibility, bearing in mind that life is full of ambiguity when making decisions. Marriage is not without its shortcomings and flaws. One should assume that the suitor might continue to be attached to pornography after marriage, and then assess one's ability to deal with this flaw. If it cannot be endured, then it is better not to marry. If it can be endured in exchange for the suitor's good qualities, then perhaps it is better to proceed. The inquirer's age and her other opportunities for marriage should be taken into account. In case of indecision, one can follow intuition and psychological inclination after performing istikharah. If the decision is to proceed, then the suitor should be helped to overcome the problem and guided towards recovery, while overlooking and not monitoring.