Is it better for a young man to strive to get married, or should he wait until his unmarried elder sister gets married, especially since their father has passed away?

It is better to marry to protect oneself in an era where tribulations abound, while also helping sisters to marry as much as possible. There is no harm in offering marriage to a righteous and competent man, as the righteous man offered one of his daughters to Moses (peace be upon him). The pious predecessors used to offer their daughters and sisters for marriage to help them maintain chastity. And Allah helps His servant as long as the servant helps his brother.