I hear your deep fear. Fear is the most crippling and paralyzing of emotions---along with deep grief---in our lives with our difficult children, I believe.
And you have both fear and grief that you are operating out of, because of the loss of your precious son. I am so sorry for your loss.
It's so hard to stop, and I understand why you have done the things you have done. I believe most of us would do the same thing, and we have, even without the loss of a child.
You sound like you are close to being done but are afraid to be done. As you near that point, and start stopping doing the same things you have always done, hoping for that change, but never seeing it, you will likely become even more afraid and sad.
Your son will not like the new you and the new boundaries. You will not like them either, because it is so uncomfortable and lonely to do something so completely different. Enabling is awful, that life, but it is familiar. Saying no and learning how to live in loving detachment, is also awful for a long time and it is very strange, and counter-cultural. Most people don't understand it.
So there is a lot of push-back, from ourselves and from other people. It takes a lot of hard work, support and using daily tools to have a chance on consistent change.
But it's worth it. On the other side of enabling is a better way of life, one that has peace, serenity, deep relief and contentment. At first those periods are brief, but they get longer and longer the more we work. And then one day, we cross the center line and the periods of good things become much longer than the periods of bad things.
Start on the road. You don't have to change everything overnight. Just start by changing one thing and living with that for a time. Then move to another thing. Reclaim your life. You deserve as much as your children.
We care here, and we understand. Keep coming back.