I take it you are baptized? I would be very careful about what you write, wouldn't they show it to an elder?
I'm sure his parents do love him. That does not negate his wanting out of this dangerous and deadly cult. In fact it should show him just how cultish it really is that his parents will disown him if he chooses to leave. I have a difficult time with posters here who always say, 'they think they are doing the right thing', 'they are sincere', so what? So was Hitler and other dictators, they were just as sincere, it doesn't make them any more right than the jw who professes love but only if..... They are spiritually and emotionally abusing him as do all jw family members who shun because someone chooses not to live their life by the dictates of a bunch of old men in NY.
From reading numerous stories here and elsewhere I would suggest a back up plan and start saving and hide your money. Try and do as they wish while you are under their roof but that does not mean you shouldn't still research. If they have the 'truth' they wouldn't mind close examination. Truth does not fear scrutiny. You could one day try and strike a deal (not likely they would agree) to read with you the C of C book.
I wish you all the best. Seriously consider finding someone who will take you in if it comes to that. A local church will help if you have no other options which it sounds like it may be the case as they do not allow you 'worldly' friends?