Well Jack, you certainly gave me a lot of information and I applaud you for your frankness and sincerity. We all make mistakes, some are worse than others, but your life is your life to live and no one can tell you what is right or wrong for you.....only you can make that decision.
With that being said....there does seem to be some sort of karmic debt owed to this woman. This angel that helped you when you needed it the most. The fact is, you can still help her, maybe she wont drive a BMW, or live in the biggest house on the block, but you can still help her get a nice car and a nice apartment, and not leave her high and dry, which it doesn't sound like that is what you want to do, if I'm hearing you correctly.
It's just a matter of standing up straight, and being a man and telling her, this is what's going to happen. Sure it's going to hurt, and she may get upset and cry...who knows. In the long run, it's more fair to her to allow her the chance to find someone who will really love her, for her. You can't stay with someone out of obligation, no matter how well intented it is. It's not fair to her, and it's not fair to you.
You've been through a lot, yes....many of us have....but you're still here, and you still have a heart and a soul. You just need to find direction, and passion. Do what you need to do what you have to do to make you happy. What you have to be careful of is falling back into the same trap all over again should you get lonely. I'm sorry to hear about your son, things will only change in his life when he is ready to change.
I think you already know what you need....must.....do. It's just a matter of time. Check with your lawyer and find out what you need to do, to sell what you need to sell, to be fair to her, but more impotantly to at least be able to walk away with something for yourself. Help make sure she gets her citizenship, you owe her that much. After that, just try to be happy. Try to figure out what it is that Jack wants to do with his life. The new life you want, can start right now, this very minute as you are reading these words, you can take a deep breath and make the decision to change your life forever. I have faith you can do that, but what matters more is if you have faith in yourself. Do you?