I can only try to imagine how you are feeling, and i would fail. Please know that you did the right thing by calling emergency services to help on Wednesday - it was not safe for you or your boys for you to try to deal with that alone.
I'm so sorry you don't have support closeby, but i really hope you will use the resources Sophie has posted to you, they are there to help you.
Is the psychiatrist your son has been seeing able to assist or advise in any way, because this is reaching breaking point.
Two of my close friends have had similar experiences to you, both of their sons are on the Autism Spectrum and specialised help was essential in dealing with their issues (as well as providing respite for the rest of the family) - this may not apply to your son at all, but i thought i would mention it.
You have come to a plave full of compassionate people with many different experiences, and i am so glad you are here.
You need support and care and love just as much as your son does, and you have come to the right place.
We're here to listen and support you.