I wish I could say your story is unique. Sadly, I can't. Many spouses walk out. Your husband did, my wife did and thousands and thousands of others. I'd like to say that the fact that you are in dire straits economically is unusual. That is more common than not these days for those of us with disabilities. States are broke, insurance companies are self-serving and inhumane and it seems almost everyone is stressed these days.
So simple acts of kindness and compassion are more precious.
Certainly the external reality of your life is what it is and how to make changes is way beyond my tiny skill set. But the other thing I read in your post are emotions that cause you great dis--ease. It sounds like you are angry/scared/resentful/scared and maybe a little more scared.
Of course you come by these emotions honestly and almost anybody in your situation would have those emotions. But whether they are "legitimate" or not, I wish for you what you wish for you – more ease in your life.
And, like the rest of us, ease is not a state of being, it's an experience we have that comes and goes.
Barbara, I don't know of anything that can make these painful emotions go away. But there are ways that you can feel these emotions and let them go. These emotions don't have to be the driving force of your life.
You said that "at least I have some form of love." That speaks volumes about who you are, what you long for and what your son and his girlfriend are capable of. Love. My suggestion is that you work on love. Try to love your son even more than you do already. Try to notice how his eyes look when he's tired or how he holds his shoulders when he is stressed. Notice the corners of his mouth when he is happy. And try to do the same with his girlfriend. Work on love dear Barbara. Love them better and then you will have much more love in your life.
Your situation won't change. Frankly, it sounds awful. And your anxiety may not ever go away. But having more love in your life certainly improves the quality of one's life. So I wish you great love.