Have you both been tested for POTS. Your descriptions remind me of who I was 3 months ago. For over 3 years, I had significant PEM and major exercise limitations. Finally, my Neurologist tested me for POTS (Tilt Table Test), diagnosed me with POTS, and now, I'm taking a med called Pyridostigmine. I am back to my full energy self. A friend reported that she heard on the news that Long Covid patients are diagnosed with POTS 5x more than the general population.
Hope this information helps.