How can one deal with the pressures from parents who object to leaving one's job and wearing the niqab and devoting oneself to Islamic knowledge, especially given that the husband encourages this?

This world is a place of trial and tribulation. Remember that reward and accountability make it easier to tread the path of the hereafter and to patiently resist one's desires. Honoring one's parents is obligatory, even if they treat one poorly or unjustly, but it is not permissible to obey them in disobedience to the Creator. You must seek Allah's help and obey your parents as much as possible without disobeying Allah. Supplicate for their guidance and success, be a good example, and enjoin your parents to do good and forbid them from evil with gentleness and wisdom, without violence or abuse.