As a person with a similar background as you, and living here in EY, I have not thought to go back to America to live, but if I did, I would strongly suggest a pilot trip before you and your husband pack up and just move (I hope I am wrong in understanding that this was your plan from your posts).
You have much to consider, including having a job lined up for your husband, and schooling lined up for all of your children. Don’t forget about a visa for your husband for working purposes if he does not have American citizenship. Many places may not be able to employ him for this reason. I don’t think you can even consider Toronto or anywhere in Canada because from what I know they have very strict restrictions on working without citizenship in their country. Have you thought about looking into the situation in the UK? Your DH will have an easier time getting work since he’s a citizen.
You will probably also have to consider getting a job since expenses are so much higher in the US than here in EY. I have to work even here, how much more so in the US.
Once you get some ideas, make a list of possible places you would be interested in sending your SN son and contact them before you spend $ on the flight over, but do come and check into things before bringing the whole family. Things appear different in reality than they sound on the phone.
As far as your other kids, do find out about the BT community and how well they are integrated. You don’t want your kids going to BY and chadorim and finding themselves segregated based on their backgrounds.
I hope your transition goes well and you find the right solution for everybody in your family.