What is the ruling on remaining in a job where the employee is forced to steal, and what is the legitimate course of action regarding not submitting a resignation and the resulting violations?

You are not permitted to steal from those who come to repair their phones. You must advise your employer to repent. If he does not desist, then you must leave this job and seek lawful employment, even if it means leaving the country. You must return what you have stolen to its owners or their heirs. As for the last question, we have no knowledge of the requirements of residency laws. We advise you to fear Allah.