Hi and welcome to HCM.
I am sorry about your father and his serious diagnosis.
This is obviously terminal stage of malignant disease. If his cancer is inoperabile nad he needed ileostomy
this means that his therapy is only palliative. It is hard do predict anything in such cases,but he will probaly pass away cause of respiratoy failure caused by obstruction or infection. So when you notice difficult,shallow breathing
, confusion, somnolency,extreme weakness and rapid weight loss
these are signs of final days.
Wish you good luck sir.