You're using Godot right? Did you try putting "Default Playback Type.web" to "Stream"?
The docs have a warning that it might cause crackling or latency but it has usually fixed my problems for web build audio.
(oh you mentioned filters those don't even work unless it's set to stream so maybe you tried it already?)
Yeah I think those things you mentioned would help a ton to make the game feel even more polished. Great Job!