Would it seem presumptuous/ jerky/ somehow inappropriate for me to buy a gift for this guy?

ha ha...i like the valentine day recomendation. Honestly, i like people life bc im the same way. Im very detail oriented and i like to express my gratefulness to people etc. So in essence, i dont think theres anything "wrong" with you getting him something, its what youre thinking about thats the problem A gift car like itunes seems too personal. Almost like, "when you're downloading music, i hope you think of me". I feel like you should get him something specific. Like a nice luxury pen or mug or somely else thats manly without being cutesy. Maybe a cool coffee thermos or something. Or a bottle of fine liquor. these things might be $20 or so more expensive than your original idea but i think they will work. hope i could help!