So, I was on the phone with my mom asking her about the drugs and treatments he has been given. She said the Dexamethasone is a red flag that this is a downward progression of his treatment. At the very least he is on "supplemental oxygen" when getting these drugs and says they would never give "high dose steroids" if they are just on "room air". If he was just on room air then why would they "continue to escalate treatment" if it wasn't escalating. These treatments and drugs hint he had significant drops in health. Also, the fact that he immediately had issues breathing and lower SO2 stats is a sign that he probably got a high viral load as she mentioned she has read research and accounts of people who have the good day and then sudden decrease tended to be patients who received high viral loads.
She said she will send me some papers she has read about COVID treatments in a bit.