You've got all your supports in order IAD, you've got all your tools and you're putting the focus on you as best you can. Good job. It's as if we have to retrain our brains and our thoughts to get off the vigil we've been holding for our kids for so long.
I read that when we continue to think the same thoughts, in particular ones around fear, it's as if we create a new neuro-pathway in our brains that the thoughts then naturally follow. What needs to happen is for us to create a new pathway, with new thoughts, so that we don't automatically go right in to the fearful, usual ones. That takes effort. But it can be done. Make a conscious effort to observe those thoughts and shift them when you can. I did that, and over time, I got myself out of that familiar way of thinking I had been thinking for a very long time. Meditation helps. So do things like yoga or Tai Chi, where you relax the mind. I really like reading books and watching videos and listening to CD's by Eckhart Tolle, he reminds me to let go of those thoughts. Whatever or whomever you can find to help you do that will assist you in letting go of thinking about your son and his issues all the time. Hang in there IAD, it's hard, but you're doing all the right things.