You tell me that your patient prides himself on being obedient to the enemy. It may surprise you to hear this, but his obedience may be a character trait that plays well to our cause. Our Father created something called legalism that I think will be a perfect fit for your patient.
In all manners of temptation, it is important for you to remember that your main goal is to win over your patient's heart and thus his soul. If you concern yourself too much with his actions, and less with his motives behind those actions, you may often find yourself discouraged for no reason. Humans who obey the enemy for the wrong reasons are just as useful to us as those who live in complete disobedience. The enemy puts an infinitely high value on people's motives. Not only does he heap incredibly burdensome commands upon his followers, but he then tells them to obey him as if there is no burden, as if their affection for him will remove the weight of those commands. It's preposterous. It is impossible to not feel the full weight of one's own burden, yet you must take care to remind your patient of this as much as possible.
Keep your patient constantly aware of all the rules the enemy requires him to live by, and overwhelm him with the length of this list. Impress upon him the fact that the enemy demands far too much of him. If you put the burden of obedience fully on his shoulders, he will without a doubt crumble beneath it (and you must be there to catch him when he does). Even if he remains obedient to the enemy, if his focus is on the act obedience and not the enemy, then you are doing well.
Now in the meantime, if you find that your patient is willing to bear the burden of obedience, you must attack his reasons for doing so. What you will find is that human motives are quite susceptible to our deviations. Again, I cannot impress the importance of selfishness upon you enough. If your patient is obedient to the enemy for his own gain, we have won. It's quite simple. Let him obey all of the enemy's commandments. Then, let him sit a little higher in his chair on Sunday mornings knowing that whatever the preacher says is beneath him. Let him listen to the confessions of others and be happy that he is above the sins of those around him. Encourage him to compare himself to others and bolster his pride by showing him how good he is at obeying the rules.
There are few characteristics that more closely resemble that of Our Father than self-righteousness. If you can say your patient is sanctimonious, he is much closer to our side than he may think, and I find few things more enjoyable than when a human dies and is shocked to find himself here with us. The humans who are self-righteous never expect to find themselves down here after death, but they almost always will. Do not fear if your patient is obedient to the enemy. Obedience for obedience's sake is to our advantage. The humans who believe their behavior is what brings them closer to the enemy are almost always more like us than they think. The battle we fight with the enemy is one for the heart, and if your patient focuses on his outward behavior, he leaves his heart unguarded and it is as good as ours.
Do keep me updated on your patient. Hearing your questions and concerns brings me back to the days when I was a new tempter. Obviously, I was not as naive as you are, but writing these letters keeps me young. I almost enjoy it.