Is a wife permitted to obey her husband in removing her hijab and ceasing to listen to religious tapes, given his threat to send her back to her home country if she does not obey him, and her fear for him and herself should she leave him in an infidel country?

The hijab is an obligation upon believing women, and it is not a matter for compromise. Obedience is only in what is good. You must explain this to him kindly and seek Allah's help through supplication for him. His threat of travel is not a valid reason for you to obey him in abandoning the hijab. Your obedience to him in this matter would be a trial for you and for him concerning your religion. Your steadfastness to this principle is better for both you and him.