Should he continue supplicating to Allah to quit masturbation after Allah has blessed him with a righteous wife, knowing that he tried by all means and did not succeed?

Supplication (Du'a) is one of the most beneficial and impactful means for attaining what is sought and repelling what is feared. It is commanded, as Allah Almighty says: "Call upon Me; I will respond to you," and "I respond to the invocation of the supplicant when he calls upon Me." You must frequently supplicate to Allah to grant you repentance and enable you to abandon this reprehensible act, and do not tire of supplicating. Furthermore, you must also utilize supporting means, such as enjoying your wife when lust arises, adhering to remembrance (dhikr), associating with the righteous, and staying away from provocations.