What is the ruling on money earned from working in tailoring women's trousers that may be used for sin, and is the father sinful for working in boiler maintenance at the same company?

You have done well by abandoning the work of tailoring trousers that are likely to be used in disobeying Allah, in accordance with His saying, "And do not cooperate in sin and aggression." However, if they are used in a permissible way, such as being worn under an abaya, then there is no harm in selling or tailoring them. As for your previous salary, there is no blame upon you due to your ignorance of the ruling. Your father's work is also permissible, as long as it is not related to tailoring these trousers.