Yeah, there's a lot of little quality-of-life things that are missing. I honestly didn't think the game was as merciless as I am being told it is.
For the audio problem, was that through browser play or download? Godot for Browser has a ton of weird audio issues that can't really be solved by devs; Browser build strictly uses "chunk" audio and it screws with how audio is played back internally. There's "fixes" for them but those create whole new problems. So it doesn't shock me if it was getting weird over time. But if it's the download version, that would be new.
Also, thank you about the music and graphics! It was meant for my other game so I put a lot of thought on how 'loopable' it had to be. So I'm glad it is enjoyable!