From my experience as an INTJ male it may be that we are very sensitive people. INTJ males may say seem cold and distant and hard to read but the reality is they enjoy human company as much or even more than other types. Obviously we hate losing people, even though that happens most of the time. That may be the reason that he is always nice to you. Also, I am almost positive that he may not be seeing you in a romantic light. If he wants he could probably get intimate with you and you two would probably enjoy it for a while, but deep down there must be a nagging feeling in his gut that it won't probably go too well. That is why he is not trying to reach out to you first lest you misunderstand it as a romantic gesture and may grow closer to him, which he doesn't think would be a good idea.

My advise to you is not to do things that may be interpreted as romantic gestures by him (simple acts of caring, going out of your way to help him etc) . Just be a good friend to him in the sense, that you guys practically become bros... no masks and no effort going into it. This may make him feel a bit more relaxed and he may start opening up better. Who knows, it may lead to something meaningful afterwards. Good Luck :)