Undiagnosed: chest tightness and pressure in head

For the last 3 years my male partner of 8 years, who appears perfectly healthy, has been plagued by unexplained symptoms that even the Cleveland clinic, which he has visited on 3 different occasions, cannot diagnose.

One evening In September 2022, then 25 years old, he went to the ER because he was having chest tightness. This is the first time we can remember him having an onset of symptoms. From this time forward, he has experienced the following symptoms every single day
-a feeling of light chest tightness around his heart
-feeling of pressure on the left side of his head near his temple
-tingling in his face (this was a symptom that occurred for about 2 years and recently died down the last year, basically no longer happens)
-chest/arms will turn quite red at random, his body looks flushed, this is a newer symptom and does not always occur every day or with the pressure or tightness so we're unsure if/how it's related

The symptoms occur at random, and don't always occur all together, but occur every single day and always without fail before bed. He has had multiple tests via the Cleveland clinic and also at One Wellbeck in London to no avail. All results present normal. He has had a full body ct scan and a head scan and wore a heart monitor, Drs think it likely is not heart related. I know that these symptoms are not imagined, they occur at random regardless of his level of focus or distraction, stress, anxiety or relaxation (which I am very familiar with as I had been dating him for 5 years prior to their onset).

He had the Pfizer vaccine but had Covid 19 twice (July 2021 and Feb 2022), he was born with high cholesterol and takes medication for it, otherwise entirely healthy.