One thing that turned my anxious, sensory, Asperger's child around was swim team. The water is great for sensory needs. The tasks were great for his anxiety (he set small goals and overcame fears and felt great about his accomplishments over and over again).
Started with 1 hour a day for four days a week at age ten and now at age 14 he does 3.5 hours a day for 5 to six days a week...over the summer twice a day some days. Days he misses practice he isn't as centered.
Not saying swimming is your answer...but find an activity with an understanding coach, one that is a good match for him, and the ability to drop him off. That one hour break was exactly what I needed. Randomly I watched and took pictures. Anxious kids need hard exercise. Anxious kids' moms need a break.
I also agree with "daily living skills". Laundry, basic cooking, sweeping, weeding, we have no snow here but I would think snow shoveling, pet care....all those things take the time to teach, do the task with him, eventually have him do them independently. I think it makes people less anxious when they have skills and responsibility that make them feel good about contributing and less of a burden.
When I homeschooled (and every summer) I have quiet hour right after lunch.... Everyone In his or her own room, alone--reading, writing, napping or non-electronic quiet playing (such as quietly playing with Legos) are the only activities allowed. We set a timer and everyone is so much less cranky with the forced quiet in the house for that hour. It is rejuvenating. We get along so much better and I get an hour where I am not the cruise director (or referee or hand maiden)
This is eerily true for my dd too. They had a week off of swim practice over Christmas and she was a hot mess.
