I have never lost a parent, but my aunt and uncle suffered from a hereditary disease that rendered them vegetative towards the end. They both went into care homes, and I can totally relate to how scary that can be.
It sounds so difficult, I know, and a little harsh, but you really have to learn to accept the situation, because it's not going to change.
All you can really do is show your dad how much you love and care for him, and try not to be too scared of what may or may not happen.
It's such a cliche but you really need to be strong for him.
-------
Maybe I will never be, all the things that I want to be,
Now is not the time to cry, now's the time to find out why.
I think you're the same as me, we see things they'll never see.
You and I are gonna live forever.