Is merely wiping the glans with water sufficient to remove ritual impurity, and is it sufficient to run water over one's hand and then wipe the glans with it? And how much water did the Messenger of Allah, peace and blessings be upon him, use for istinja'?

Washing away impurities with water is not enough; rather, water must be poured over them until they are submerged. Wetting the hand and wiping it over the impurity does not purify it. It is established that the Prophet, peace and blessings be upon him, used water for ablution (istinji'), but the exact amount of water he used was not specified. It is not obligatory to use water for istinji'; rather, it is sufficient to wipe away the impurity with a tissue or similar material after it has ceased, though water is superior.