All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
Firstly, we would like to congratulate you for embracing Islam. We ask Allah to help you adhere to steadfastness on the truth and guide you to be a reason to make others receive this blessing as well, especially your family and relatives. Verily, this is one of the best good deeds that draw you closer to Allah. The Prophet, sallallahu ‘alayhi wa sallam, said to ‘Ali, may Allah be pleased with him, when he sent him to Khaybar, “...Then call them to Islam and inform them of what Allah has enjoined upon them. By Allah, if a single person embraces Islam at your hands, that will be better for you than the red camels (the most precious kind of camels).” [Al-Bukhaari and Muslim]
Your father has no right to oblige you to work, and you are not obliged to obey him in this regard. The child's obedience to their parents is not obligatory in all cases in an absolute manner. Rather, it is restricted to what is in the parents' interest and does not cause hardship to their child. Please refer to fatwa 131695.
Also, your father has no right to demand that you pay him back the money that he spent on your education; scholars stated that the father is obliged to provide education for his children and to teach them a craft. The Maaliki book Minah Al-Jaleel Sharh Mukhtasar Khaleel reads, “The father or any other guardian should tend to the needs of the child, male or female, under his care; this means that he should discipline him and send him to a school (i.e. a place where he learns how to read and write or a male or female tutor...).”
The Shaafi‘i book Nihaayat Al-Muhtaaj fi Sharh Al-Minhaaj reads, “He (father or guardian) is obliged to send him (the child) to a place where he learns how to read and write and to a place where he learns a craft or trade according to the child's conditions...”
Our advice to you is to be patient with your father and to try to appease him and avoid his evil to the best of your ability. You should also supplicate Allah frequently to help you against him. You can seek the help of some people who are close to him when needed.
Allah knows best.