This doesn't mean you should dump him by any means! I certainly wouldn't do that. I have so many walls up, that it's very hard for me to open up to people about my innermost thoughts and feelings at first. Also, if he came from a family of Sensors like I did, he probably outwardly acts much more like them, since that's the best way he could fit in. INFJ's can usually change their outward personality type fairly easily by studying those around them, and mimicking them. It makes it easier for us find our place in society and the world...you know, the whole seeking perfection thing.
What I would do is bring him alone to a location conducive to deep conversations, such as a park or nature setting, a library, or a coffee shop when it's slow, and just talk to him. Once you get him away from all of the S distractions, you might be surprised at how much he opens up to you. If you still find it difficult for him to talk about those things, find a topic that you know he enjoys, and start by asking questions that will lead to those deeper topics (making sure the topic makes the transition fairly easy). I've always found that talking about anime, sci-fi/fantasy, and faith activity (if there are any), are all good openings.