I'm an older poster, under a different name, which I'd rather keep hush hush. But I've been following you for a while.
I think you are trying really hard and have done a lot for yourself. Doing everything alone is very difficult and overwhelming, but you are doing it!
Some things that are noteworthy and I feel are worth posting about (when I haven't posted in almost a year to anyone) is your anxiety. Anxiety is real and it can certainly be debilitating. The anxiety you feel before your job, well, most likely isn't the particular job. Seems to be a bit high stress, yes. But the particular things that give you anxiety with this job are normal for EVERY job. Deadlines, upper management pressure, office hours feedback....... you are going to get that everywhere.
So, I was thinking of some options you might want to consider. First thing you can do is properly manage your anxiety with the right meds. Do you have health insurance? Perhaps seeing a psychiatrist who can prescribe will help you manage the ups and downs and the anxiety, ALONG with ADD, along with behavioral techniques. Going on and of AD's is only going to hurt you. Especially when you manage them yourself. The right balance of the proper meds would probably go a LONG way for you.
Another option for you, surprisingly enough, would be a very structured job. I believe you think perhaps more freedom is best for you, to work on your time, but looking from the outside, I think deadlines which need to be met when you are freely managing your own time are giving you is causing you to get way overwhelmed. Perhaps a job that has concrete hours with a concrete job description would give you no choice but to get what you need to get done. Don't get me wrong, there will still be pressures for completed work, working to your full potential, and feedback, sometimes good and sometimes bad. But sometimes someone else giving you all the tools to get the job done, helps.
There are also things you can take off your plate, I have mentioned them before, and I wont mention them again, although you look like you are considering and looking into it.
And don't look at things as impossible tasks. There is nothing impossible. Everything is doable. You just have to look at them that way. Start putting the UNECESSARY tasks away in a drawer for a later date.
I wish you luck as always. I see good things for you, but you have to try to stop getting in your own way:)