IA,
I couldn't agree more but the problem is legally it might be too little too late. I'll be painfully blunt.
First, you handed over custady to your parents and two he is is now of legal age. You have nothing to say about "his decesions" now.
I don't think there's a damn thing you can do now, however tragic it is, except contribute to bringing the C of $ down or if that doesn't happen and he decides to blow, he needs to know how to contact you.
At that point, you're going to have invest as a parent what you did not invest in before; he will need your help to relaunch his life.
Sadly, it is too late, but when you read the entirety of IA's story, he did nothing wrong. He honestly believed he was acting in the best interests of his son and family. Realities have changed.
During the time that I was involved in the Property Market, I had a simple piece of advice for couples looking to buy a live-in home and an investment home--buy the live-in home in her name, and the investment home in his name. Marriage used to be "I do, until death do us part." These days it's, "I do, until I don't." And as Aus family law usually gives the matrimonial house to the woman it makes sense that the estranged man has the investment home to move into at his earliest convenience.
So it is with Father and Son. IA acted in the best interests at the time, believing that his son would be properly looked after and hoodwinked by the cult into thinking that everything was "OK"--yeah right!
I like IA's letter to Shane. It is slightly 'nostalgic' but simple. It contains no negatives for the Sea Ogres to censor, and I've privately forwarded some positive ideas to IA so that he may attempt to build a legitimate Father/Son relationship.
Naturally, it will not be the relationship that the rest of us "think" it should be. My own relationship with both my parents was "unnatural"--and relationships change--after a number PMs between myself and FreeThinker, we swapped email addresses and had a great rave, but then we ran out of things to say...
Please support IA, pray, carry good postulates, what praseology works for you so that he may be able to get back part of the Father/Son interraction that has been sadly missing.
RPX