If Alanon feels right for you, stick with it. You will learn how to set boundaries; through listening to other people share, you will find your own story (or variations of it) described by many people, and that can help to give clarity, too. It's also enormously reassuring to realise we're not alone.
For now, don't concern yourself with what he is or is not doing, how his parents are reacting, or what he's hiding. Recovery is something we do for ourselves, and that applies to both you and him. So, just for now, concentrate on being nice to yourself, and participate in as many self-nurturing activities as you can.
(((HUGS)))