When I read the totality of your posts, it appears you are very focused on even minor issues.

All of your symptoms can be caused by anxiety. You sound detail oriented in a way that is common to intelligent people. The combination of focus on details and intelligence makes even very minor PCS symptoms much worse. As that brain tries to make sense and struggles to do so, anxiety levels increase. They may not manifest as common anxiety but rather a sort of obsession of thoughts about 'what is going on.' This can be exhausting and the stress can cause increased symptoms levels.

I used to have thought overload, not about trying to understand my symptoms, but rather, my mind would get stuck and overwhelmed in repetitive mundane thoughts. It would take me a few days to recover.

You could do some assessment on your own with a home blood pressure kit. If your symptoms parallel an increase in blood pressure, that could be a indicator of anxiety. I have Klonopin and propranolol (beta blocker) for such events, depending on the trigger. I prefer the propranolol as it does not make me drowsy.

Your caffeine sensitivity suggests possible anxiety since caffeine increases anxiety.

Have you ever had any hormone or neurotransmitter testing done ? Adrenaline, cortisol, the sex hormones, thyroid, GABA, etc. You could have an overactive response in those areas. I struggle with adrenal cortical hyperfunction.

Are you taking any supplements ?

What do you do to moderate over-stimulation ?

btw, I can be overstimulated by phone calls, especially if it is an animated conversation. I also know what serotonin syndrome is because I lived with a mild case for 14 years from max dose SSRI's.

Time to take my gabapentin so my system will settle down so I can get to sleep in a couple hours from now.

My best to you.