I found this software a couple of days ago. Not sure if it will really help with your first problem 😆 because I'm still figuring it out myself. But looks promising.
https://github.com/wwmm/easyeffects
For me, one of the most memorable was, beating Ornstein and Smough in Dark Souls for the first time solo. It was a great feeling of accomplishment, and I could see that I really mastered that game's combat.
You get downloads and subs with NewPipe, too.
But it boils down to preference. And I prefere a open source app to begin with instead of patching something.
Based on the screenshot I assume that you used youtube premium lite (what ever this was...) on your smartphone. Therefore, here the obligatory recommendation for NewPipe. Quasi Youtube Premium as apk.
It has all the features you need:
no ads
you can close the app and your videos keep running in the background
you can turn off the screen and your videos will continue to run in the background
There is also the fork NewPipe x SponsorBlock (link to repository) which integrates SponsorBlock into the app. (duh...) This will also skip the creator's ad blocks in the video.
That's gotta be the cyberpunkiest thing I've read in a while.