Its early days too, but I want to start ASAP, so anyone have some ideas, or experiences they can share?
Well, I like how you stresslessly, naturally transformed the situation into something that reduced/removed your charge's stress:
I began matching his vocalizations, and then turning them into a "Funky Drummer" beat box kind of rhythm.
This is super-key, transforming vigilance-stress into a non-stressed state via a stressless game (in which
you feel stressless and content; your charge will model your authentic state if it is safe and at ease), not by lecturing or harsh "no-no"ing (which you didn't do, but I want to be clear). The learning your charge gets is really from your role-modelling and whatever you are authentically feeling. So if you're also working on calming any aspects of your own diagnosis (e.g., concomitant anxiety), this may help you, too, to develop deep ease.
Long, slow deep breathing is a great instant help, a great game: counting 5-sec inhale (or longer), and counting 5-sec exhale (or longer). This will take any locking up of the mind into the brainstem (where fight-flight-freeze are the reactive states available) and calmly help information pass through the brainstem again (so that the whole brain can be used again). If you add a calm physical motion to the breathing, like raising and lowering arms over head, this apparently restored whole-brain use more quickly and when in conjunction with the breath. So this breathing game is a "fast" anxiety reducer (unless it's rushed and you feel stressed), but needs to be a regular practice, preceding a perceived threat event.
Humans are similar to horses: a prey species that herds together around the safest, confident, easy order-keeping member. So my guess is that in a year or two with you ~ if you feel reliably safe and calm to yourself, then he'll also learn to size up situations like you do, based on your own authentic role-modeling. Cause-and-effect (aka: interbeing, contingent identity, dependent origination) applies here, too; meaning, you two are co-creating each other as you relate. it's just that the exchange of co-changing each other may take longer than co-changing occurs between you and more socially-engaged people. So what might take an hour or a week to learn by just living around someone who is socially engaged, this can take days or many months for someone who has a strong just-own-senses engaged world and not much interest or mental development in social engagement. Staying safe, at ease and enjoyable are the keys to any rapid learning here, imo.
The weird thing is he HAS incredible, almost jhana like concentration abilities when he's absorbed in some activity that he's interested in, but he's constantly switching his object of attention, so he's like a laser pointer going from one display to another to another etc.
Yes. (Kim Peek and the like have been so key in showing extraordinary feats of mind despite other areas of retardation; let's not "cure" these minds...). You could try a game of "five senses", having specific times in each hour where you ask your charge to point out something happening at each sense door -- this could get your charge to move attention from narrow to enjoying broad focus moments. The brain likes to do what it does well already, so if your charge is addicted to repeat behaviors, some of that is because there's pleasure in the brain doing what is familiar (well myelinated) to the brain. So a new 5-senses game has to be stressless for you (who he will be modeling and detecting your authentic comfort or lack thereof), like what you did with the beatbox idea, naturally enjoyable, else learning something new will be stressful and rejected.
What do you think?