"I have strange feeling in my wrists and ankles often, in that I have to rotate them a lot in order for me to feel them properly."

This is something that I do too! i used to think it was just because I had sprained my wrists a lot as a kid (very clumsy and unbalanced, even today at 19 yrs old), but the more I looked into it the more it seems like a stimming behavior. The more calm I am, the less I do it. But even when I'm calmed and I'm laying under my heavy blanket, I still do it occasionally. It's become both a habit and a stim for me, but sadly it doesn't seem to help do anything other than give me sore wrists.

On topic though, the stimming of your son probably increased when the stimulation around him increased. Stimming is a way to try and 'take control' of the input around you, and try to organize it so to speak. If something lightly brushes against your arm and it feels like ants crawling over you, arm/hand flapping will send vibrations through your arm- that you can control- to counter that antsy feeling. Humming to self or babbling loudly overpowers outside sounds because what you hear from your own voice tends to be 'louder' than environmental noise.

I just ordered and received my weighted blanket, and although I haven't seen an OT yet, I've already seen how it helps me. I can get to sleep easier at night, and in the morning my body isn't so low that I can't wake up without dozing off 10 more times during the morning. I can finally get up, lay under my blanket for 10 mins, do a few joint compressions to wake my body up a bit better, and then start doing normal morning activities. We'll see how much this helps come school time for me, at least.