Is it permissible for me to work and study in a mixed environment while wearing a long jilbab and khimar without covering my face and hands, with the intention of completing my studies and traveling to work in a non-mixed place, especially given my significant contribution to my family's expenses and supporting my parents, and my husband's threat to me when I tried to wear the niqab?

We have previously clarified the permissibility of women working and studying under specific conditions, including the absence of unlawful mixing, and adherence to complete hijab, which, according to the preponderant opinion, includes covering the face and hands. If you are compelled to work or study, there is no harm in continuing while not wearing the niqab, provided you refrain from sitting with or socializing with non-mahram men. As for your husband, if he is an apostate and remains so, you must separate from him, and it is not permissible for you to live with him unless he repents to Allah. In that case, you may return to him with the original marriage contract as long as you are within your iddah (waiting period); otherwise, a new contract will be required. The obligation is to advise him to fear Allah, to improve his Islam, and to observe Allah's commandments, especially prayer.