Hi Mukk_in,
I am so sorry to hear of your loss. I cannot begin to comprehend the enormity of losing your dad and also dealing with the struggles of your mum with this terrible illness.
I lost my grandfather about 10 years ago and he was an atheist/evolutionist all his life. I cannot be sure if he really did change his mind in his last hours (I am told he did), however, i hold onto the following hope...
Jesus said in Matthew 7
9“Which of you, if your son asks for bread, will give him a stone?
10Or if he asks for a fish, will give him a snake?
11If you, then, though you are evil, know how to give good gifts to your children, how much more will your Father in heaven give good gifts to those who ask him!
12So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets.
If your parents lived by the above statement in vs 12, then i am sure that God will see the cloak of Jesus around them at the Judgment. You dad will be cleansed as white as snow and he will be among those who say to the Lord in Matthew 25...
37Then the righteous will answer Him, ‘Lord, when did we see You hungry and feed You, or thirsty and give You something to drink?
38When did we see You a stranger and take You in, or naked and clothe You?
39When did we see You sick or in prison and visit You?’
40And the King will reply, ‘Truly I tell you, whatever you did for one of the least of these brothers of Mine, you did for Me.’