It sounds like he's just extraordinarily self-reliant and independent. I'm not stating that as a "good" thing, although those traits are usually thought of as such. In this case, I do think he cares (or did at one point -- it sounds like this behavior has taken place over a long period of time).
The incidents about stating that he liked you as soon as you met, very long conversations, and responded with empathy and caring "months ago" when you were in distress all seem to indicate that he really enjoy(s/ed) your company.
The red flag here is your very first statement -- that now, if you call on him in any sort of distress, that he doesn't respond.
You mention that he stopped responding when you first got together with your (now) ex. That alone leads me to wonder if, when you first met, he thought (and hoped) that your friendship had romantic potential, and found out that he'd misinterpreted things when you got together with your (now) ex. Hence the pulling away. If this is true, it's not that he doesn't enjoy your company -- he does -- but that he's wary of spending time with you, as he doesn't want to get hurt.
Obviously I don't know either of you or the specifics of the situation, but this seems consistent with his behavior. Is it at least a possibility?
As far as the whole phone thing goes -- I'd agree that if he's not a phone person that email might be a better medium for casual contact. Being able to respond when he's ready to, where he can get his thoughts together before stating something, may help. If you really want to know what's up, you're probably going to have to ask. If he ignores you... not much you can do
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Many INTPs do care about other people's feelings and NEED to know how they're feeling but since they don't know, wonder how they themselves should be feeling and reacting, which spirals into detachment or analysis-paralysis.