Is it permissible to take money from one's father without his knowledge for the purpose of emigration and preserving one's life, knowing that he is financially well-off?

Congratulations on embracing Islam. It is confirmed that taking others' money without their permission is forbidden. Preserving your religion does not permit you to take your father's money without his permission. You can conceal your faith and perform rituals secretly until you are able to travel, find lawful employment to earn money, move to another city, or take out a loan. It is advised that Muslims and scholars help you raise money for travel, for Allah helps His servant as long as the servant helps his brother.