Hey Flyonthewall, I am sorry that you have to witness this in your son - you obviously love him dearly - and being disabled makes it even more difficult, I'm sure. As he is 32, have you had a talk with him about what is happening? It takes a ton of courage, but have you asked him if he wants to live or die? Perhaps this is his way of saying he is at his end....that he doesn't want to go on? Being able to actually admit that or feel like someone is finally listening to him might be the beginning of recovery....or at least acknowledging that he is in difficulty.
Year ago, as a community nurse, I had a client who was in her 60s and severely anorexic and her hubby and mother were so angry that she wouldn't eat....it was the only thing in her life she could control and she had made her choice....after some intervention, everyone understood what her wishes were and she passed away in peace after a long hard struggle.
I only give this case as an example, but perhaps that could be a starting point, recognizing he is in anguish and allowing him some choices. I don't mean to be offensive, so please forgive me if I am coming off that way....my heart goes out to both of you and I will be praying for you both. Blessings/L