We took my oldest out of grade 0 (K) last year with extreme anxiety (diagnosed) and it needed 9 months of therapy after 3 months of school to help him get over the anxiety, bed wetting, anger, tantrums, aggression, night terrors, zoning out, apathy etc etc.
We decided to just let him be at home playing for a while to find his centre again. It led so naturally into a continued way of life that we decided to keep at it and homeschool, but in a less formalised way. So we unschool essentially and I go about my day and he and his younger brother (4) go about theirs. When they want to do specific stuff I am there. I suggest things for each day but they are totally free to say yes or no, and they go about their own "work", right in the same room as I do my "work".
I cannot tell you how much happier he is - full of pure joy again; it sparkles from his eyes! And I got my precious, sweet, funny, cheerful little guy back again. It was a scary and dark and very exhausting time which I never EVER want to repeat EVER again. So I am happy too (And sleeping again! yay!)
You seem to know what will work best, so now you just need to take a deep breath and let it happen
Your son also needs to learn to trust his instincts and communicate them to you quickly. But its so hard for them when they are living in that situation daily
I really hope that this will work well for him!