What advice and guidance can be offered to this man so that his affairs may be set straight, and how can he defend his mother's honor?

It is not permissible to watch pornographic films or engage in masturbation that results from them. One must stay away from them, as Allah Almighty says: "Tell the believing men to reduce [some] of their vision and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do." One must repent and follow preventive measures such as marriage. If unable to marry, then you must fast, as the Prophet, peace and blessings be upon him, said: "O young men, whoever among you can afford to marry, let him do so, for it helps him lower his gaze and guard his modesty. And whoever is not able to marry, let him fast, for it will be a shield for him." As for your mother, it is not permissible to accuse her based on ill-suspicion merely by seeing a name, as Allah Almighty says: "O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin."