Is it permissible to terminate a fixed-term contract if the employer breaches its terms, and is the money earned from a new job considered lawful despite lying about it, knowing that the lie was necessary to avoid obstacles?

If the company owner breaches the contract, it is permissible to terminate it. However, if he does not breach it, then it is not permissible to terminate the contract and leave the job, due to the Almighty's saying: "O you who have believed, fulfill [all] contracts." In this case, one must repent and seek the company owner's رضا (satisfaction). And the wages from the new company are lawful if they are in exchange for permissible work.