Ambulance/police sirens are merely annoying, but due to some ear issues from when I was younger I learned about how my ear canal works and somewhere along the way I figured out how to use the muscles near my ears to apply pressure to make sharp noises 0.1% less sharp, so that deals with that.
If you want to keep in touch (via throwaway or non-throwaway email), I'm gmail@asmqb7 (decipher as per obvious). I'm curious about frequency-based health issues in general, because I wonder whether everything has similar root causes and the solution(s) for one are widely applicable to the others. FWIW I'm absolutely tragic with email (backlog months (!) long :P) but occasional back and forth of news etc may be interesting.
I'm fascinated that you have zero issues with RF (Bluetooth). How long can you use a tablet (= fanless thing with a screen in it)? Try seeing if your computer has Wi-Di (Wi-Fi Display) - it's a low-latency Wi-Fi-based display solution built into newer Intel chips. I don't have a new PC so I have no idea how it works, but if you have it it'd likely be the simplest way to solve the "can't watch YouTube over VNC/RDP" problem.
For the computer, have you tried putting it in a different room and running a long display cable and using Bluetooth keyboard and mouse? This setup allows me to use my computer for up to an hour compared to less than five minutes with it in the same room.