Is it permissible to train in law and combine two jobs so as not to jeopardize the future, despite marital disputes and the husband's refusal?

As long as you are married, it is not permissible for you to go out to work without your husband's permission or consent. If you go out despite his prohibition, this is an act of defiance (nushooz). However, if your husband is unable to provide for you, and you need to work to support yourself, then it is permissible for you to go out even without his permission.