The ads in the middle of the video can't seem to be turned off separately. I always thought that I had turned off the ads in the middle. It's not too much of an impact on the look. The ad in the middle of this video is turned off, right?
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app