Your mom isn't unhealthy? Then taking care of your father is HER responsibility. She isn't that old - certainly not old enough to have her son martyr himself over by giving up his own life. And who knows? After all those years of marriage, she may enjoy getting some time to herself once he goes. (I don't mean that to sound offensive; it is merely a reality for some women who spend their whole lives caring for others.)
You are making excuses.