It’s true the Church teaches no one is under obligation to take extraordinary measures to preserve life. The nun you spoke to was correct.
It sounds like, sadly, Mr Kasum is in such a state. It would be best if those who know him best (and don’t stand to gain anything) be the ones to make such a decision now.
It seems the daughter will gain nothing by her father’s death. If that’s true and his wife gains by keeping him alive (I don’t know if that’s the case), then that seems to be the answer right there.
He and his wife gain time together.
That’s worth more than anything else in this world.
At least for some people, the lucky blessed ones.