Is this the end of life stage? And how much longer can it last?

I just read where you were having a hard time reaching his hospice nurse. Hospice agencies are supposed to be available 24/7, and if his isn't, you might need to switch hospice agencies, as your father deserves better.

I am sorry you are having to deal with this at such a young age. There's nothing easy about watching someone in the dying process. There are many different stages in that process, including confusion, agitation, extreme pain, and not eating or drinking. Hospice can give your father some medications for his agitation, and pain, so make sure they do. Everyone's dying process is different. My husband went 41 days without eating, and about 25 days with no drink, when he was dying, which is not the norm, but that's just the way my husband was, a fighter to the end. Praying for God's strength and peace to be with you in the days ahead.

You are very, very young to be dealing with this.
Do you have any sort of support? Where is your mom in all of this? Siblings, if any?
Is dad on hospice? If not, call them ASAP. They will help keep him comfortable. They can offer support, not only to dad, but to you as well.
While no one can definitively tell you exactly how long dad has, from what you're describing, it seems like dad is nearing the end of his Earthly journey. If you're alone, you need some support here, as well. I hope you reach out for some in-person help!

First, 27 hugs to you for assuming a far too massive responsibility at your age, and having the guts to do it.

If you have ANY access to professional support, I’d get into that. Municipal Rescue Team? Maybe start with municipal police? Any other responsible family member?

The call you need to make is “breathing but unresponsive”. Police have some training in first aid then their training will lead them to contact other support.

Please post back when you get a handle on what’s going on.