I think you shouldn’t set any quantum manually. That’s just asking for trouble and burns CPU cycles for no noticeable gain. Apps which really require low latency will request what they need, usually.
Oh no, disregard my comment about that; I was misreading the log. I actually suspected that using the ALSA API was contributing to the problem and would have suggested to switch to the PulseAudio interface. You can double-check, if it’s enabled by opening about:support#media, which should say "Audio backend: pulse-rust`.
Maybe that is something to do with HDMI. Maybe this thread can help, if that’s the case: