What is the remedy for the fear that God will withhold sustenance in the legal profession, what is the limit of obedience to parents, and was what was done out of obedience to the father correct?

Working in law is permissible if you adhere to its Shariah guidelines. As for sustenance (rizq), it is solely in the hands of Allah, and a person must strive for it without transgressing Allah's boundaries. So, rest assured that your sustenance will come to you. Obedience to parents is obligatory in what is good and lawful, but obedience to them is not obligatory in acts of disobedience to Allah or in matters that would harm you. However, it is recommended to be gentle with them. If you closed your office in obedience to your father, despite suffering harm from it, we hope that you will be rewarded for this obedience.