Confronting a Gorilla...or two

My 87 year old father was rushed to the hospital last Friday with a choking cough-he simply couldn't breathe and that scared my Mom enough to get him an ambulance and a hospital bed. An extreme case for my parents, self-suffient (almost) to the end.
He's got the usual gear in the hospital, the breathing tube (optional), an IV, and all the bells and whistles that modern science uses to gauge a person's life. He gets the meals, which are just fine (although a little short on the sodium side) for him, his only problem having to get all the disposable lids off the containers. What is lacking is the ordinariness of life-there is no such thing as rthe security of a routine for him, or for my Mom or for myself for that matter. Our tiny family has lost its bearings without the sameness of everyday life. We look for it in the closets. on the television, in the food, but it's gone. It has, for all intents and purposes, flown the coop.
Delilah, that faithless hound of mine, has also lost the routine she had (if you don't have pets, you have no idea how well they keep time and monitor your movements) along with the better part of her breath (she, too, is suffering from a condition where her esophogeal tract is spasmodically constricted: in essence, her airways seem to shut down periodically). Taking her out into the cold air seems to exacerbate this condition, sometimes leaving her gasping and sometimes completely unaffected. She seems to recover and transform back to her normal self, which is a 16 year old well-loved member of the family. I crave these moments, but they are becoming less and less frequent and the gasping episodes more frequent. I have the power to end this animals life-how the hell do I know when this should happen? Of course, I can consult the vet, but it truly is up to me-to work as a monitor and a gauge to "feel" or "intuit" when the bad stuff outweighs the good-or when the pain (which is not so easy to see nor can I petition the patient) seems to be too great...but what about the suffering that is done in silence....or is it really suffering or just silence? How to know, how to know...
I know that there is a little rambling here. Please forgive me this. But searching for some kind of reason and reasoning for both of these beings is difficult. Granted, they are both at the end of their lives. But what to do for each of them. I know my Dad is getting a lot of medical attention, but the constant nag of internal questions as to whether he's getting the right care is twisting me. Delilah, one very tough dog, is a more immediate issue for me, being a cute old beggar one minute and a gasping creature in agony the next-what do I do for her? How do I know when I'm keeping her alive for the wrong reason?