Ok so the reason I asked about taking your Mother to therapy is that I'm trying to figure out how stressful this is on you. Caring for loved ones is incredibly stressful at times, but you push through because you want to be there. This is something I'm very aware of. I'm trying to establish the idea that this stress alone could be significant in your anxiety and symptoms.
Secondly, having read through your posts again I find it impossible to believe you have a heart condition causing this that has yet to be fully diagnosed. Heart disease is relatively easy to spot, and treatment is sophisticated. In America especially, the medical profession would jump at the chance of getting you into treatment. This alone doesn't make sense to me, and your 'formal diagnosis' could easily be descriptive of your underlying anxiety (in my completely unqualified opinion).
There is still nothing you have described that I haven't experienced myself at my worst and most stressed. Everything you say is familiar to me, and I'm almost 20 years older than you and was never diagnosed with any kind of heart disease either, despite being tested numerous times.
How would you describe your diet now?
You should pursue the diagnosis for your own peace of mind, but what I'm reading points towards multiple layers of stress, a mind that's tuned into the inevitability of illness and doom and a completely worn down central nervous system.
Even if you do have some kind of heart condition (and at this point it can't be anything serious), then it will be treated and you'll still be left dealing with the anxiety. Dealing with the anxiety has to be priority right now I think.