Sorry for your loss..
Get a professional medicolegal lawyer advice if you want to pursue it.. be prepared with lots of money.

But from your story, I doubt it will go anywhere. I work in medical line, and what HKL did to me seems like a standard procedure. ICU are packed, beds are limited, and turnover rate is high. If they see patient a bit stable, they will discharge the patient to normal wards.

Last time my late mother, in IJN for heart attack, was in ICU. But later stable, then move to normal ward. But then she passed away in normal ward.

These things do happen..

Sorry for your lost ts.
My case also similar but during the peak COVID time in Y2021. Before my dad passed away, we were still texting the night before and it looks the situation under control, but somehow the COVID attacked at mid night about the same timing as your dad, then went in to the ICU for rescue but can't get through it.

So it sounds quite common that COVID bring ppl life away during midnight. I think the hospital has done their best, sometimes we need to learn to let it go.