Well... knights get quests too. Let's set him one. Or eight.
Give him six months to shadow us. During this time he needs to prove himself in the three virtues he just espoused; Valour, Compassion, Sacrifice. We'll add in the rest as well; Honour, Honesty, Humility, Justice and Spirituality. These are quests he must undertake in his own time. If he succeeds at enough of them to our satisfaction, we'll take him on as our squire.
Valour: A knight must be able to protect others. Simply put, Luther must complete his basic combat training to our satisfaction. More than that, he must actively seek out an opportunity to use his strength and training to aid others in this way.
Compassion: A knight must be charitable and compassionate to those around him. Luther must devote a portion of his time each week to helping others, either through giving of his earnings as alms or by assisting local families with their tasks. He cannot refuse aid when requested, so long as their need is true.
Honesty: A knight must be truthful and open. During this time, Luther must speak truth at all times. He may keep silence out of discretion when it might hurt, but may not remain silent when his silence will do harm.
Sacrifice: A knight gives of himself to others and thinks little of the cost. Many lost as he did in the sea raider attacks, even here. He must aid the refugees in building new homes and do what he can to assist and support those widowed and orphaned by the battle.
Justice: A knight repays like for like and sees no insult unavenged, save when tempered by mercy. Luther will accompany us in court and both shadow and assist the magistrate when dealing with lesser cases. Should an incident occur when one is needed to go beyond the call of duty in the pursuit of justice, he must take up that mantle and pursue it to its end, saving that mercy should stay his hand. Luther may not engage in any unlawful or unjust behaviour, no matter how desperate the need.
Honour: A knight treats others with dignity and holds to his word and oaths. Luther must obey any oaths he swears or promises he makes to their fulfillment. He may treat no man as lesser than himself, even the most filthy of beggars or the most desperate or dark of criminals. If challenged to fight, he may refuse no equal. Luther must not engage in any subterfuge or deception during this time either, no matter how tempting, even in the pursuit of one of the other virtues.
Spirituality: A knight must be learned and listen to the wisdom of those who came before in making his decisions. Luther must learn to read and learn also the copy of the New Testament you own. He must spend a month with the monks at the Abbey (monastery permitting), living among them and learning what they can teach him of peace both inner and outer.
Humility: A knight must live without pretension to being anything other than one man amongst many. For the last month of his trial, Luther must abandon all personal possessions save a robe for modesty and journey to Torchester to live as a beggar again. He may only eat what he can find for himself or what is given to him. He may not raise a hand to any man, no matter how they insult or anger him, save in defense of himself or another.
When all this is done, then he may become your squire. And, you note, a better man than you.