Sunshine, i like your screen name, reality is, life gives us lots of sunshine, and unfortunately a fair amount of clouds as well. The latter makes the former, that much sweeter.
My first reaction to your question was, "well, 76 isn't so old these days". But then i googled life expectancy and found that the average life expectancy in India is 67 (vs 78 in the U.S.)
https://en.wikipedia.org/wiki/list_of_countries_by_life_expectancyIt's a tough question. But i think the answer, to me at least, is obvious. We all want the best for our loved one's. To wit, you are feeling like you are the parent to your parent. The question i think, is, whats your dads mental capacity. Is he fully capable of making his own decisions with a clear head? Assuming he is, it seems to me that he has a right to make his own decisions. What you can and should be doing for him, is helping him, through your research here and elsewhere, including conversations with the doctors, to be fully informed. If you do that for him, with him, you've done well by him. Sometimes the best thing, the right thing, we can do for those dearest to us, is also the hardest.
Just food for thought.