You need to tell your friend that you don’t appreciate this behaviour, and perhaps make some new friends. It’s also not your fault or responsibility if you’re in a better situation than someone else, but if you can help bring other people up that’s good.
Wallpaper engine for interactive wallpapers.
There’s mechvibes for system wise keyboard sounds (but you can’t do better than just having a good keyboard)
I’m sure there’s a Firefox extension for filters, but most browsers focus on actually being good browsers over random gimmicks so you might be out of luck. Value your privacy and your data