This cardiologist in York has a number of videos on POTS which look useful. e.g
Help with POTS and other signs of dys... - Functional Neurol...
Help with POTS and other signs of dysautonomia from Sanjay Gupta


My wife was diagnosed with fnd last year then pots this year
I watched the funny video about the sympathetic and parasympathic and as they both regulate our nervous system, I know its a balance. From my Education classes a diagram of a seesaw was used and ways to bring back the balance were suggested.
For instance, as shortness of breathe was mentioned and exercise difficult, they did floor exercises.
I do floor ex everyday, as well as ex from Lawrence van LIngen mainly to keep front of body tension free to reduce shaking. Have discovered today he promotes neural ex as well, including for the eyes .. thinking of your son here. see ref.youtube.com/watch?v=d28804F...
Did you read my last post, I read that they advise you to lean in to tremors. Thats something new I have learn't.
"A success story", interesting therapy used for tremors.