None of us can know what it's like to live with a handicapped child..mine was challenging, difficult, sometimes(when he was an adolescent) we felt we couldn't leave him alone..cos he might kill himself..
But this is different.
I do believe that the experience with your son has exhausted you and your W..I know you already know that.
I don't know a way around it. I am sure you have looked in to all resources.
I feel your sadness about him..it must be so very hard Andy.