He may be becoming disheartened from something that has occurred, or for a number of things that have happened over time. I thought some of my family might never speak to me again other than 'family business' but this has not been the case.
I would welcome his communication wholeheartedly but not mention anything religious with him at this stage. At best he may be in the very early stages of feeling that something is wrong but he doesn't know what and if you throw TTATT it may re-establish the original barriers. Make sure that he knows you can talk to him about anything and you are there, don't pressure him into telling you things that he is not ready to tell because he is unsure of his own feelings.
It sounds like he misses you and is disobeying the org. by contacting you. This is a very good sign.