Should the father be informed of what was done previously, and must the money that was taken from him unjustly be returned?

It is not permissible to take a father's money without his consent, based on the Prophet's (peace be upon him) saying: "The wealth of a Muslim person is not lawful [to take] except with his willing consent." A child does not have a right to his father's money beyond the reasonable maintenance if the child is poor. You have two options: either inform your father of what you have done, in which case he may either forgive you or demand the money back, or do not inform him if you fear a greater harm. In the latter case, you are obliged to return the money to him by any means without informing him of it. The Permanent Committee has issued a fatwa (definition) stating the obligation to return any surplus from maintenance expenses to the father.