I do not work for the USPS and I do not know anyone who does who also has hiring authority.
I can't say, never say never. I don't know. A miracle could always happen.
I just prefer not to plan my life on the possibility of some kind of miracle happening. If it happens, I am pleasantly surprised. If it does not, well I did not plan for it. Therefore, I am not disappointed.
How you plan your life is, however, your business, not mine. If you want to cling to a glimmer of hope, I can't say that you are wrong to do so.
I don't consider working at a busy fast food place as low stress employment, even if it pays minimum wage. For people who suffer from panic attacks, I probably would suggest a job with an emphasis on technical expertise, but with perhaps limited personal interactions with others. Also, it would help if there were no "impossible deadlines". Whether such a job truly exists in the open labor market is, of course, another issue. It may not.