What is our duty as Muslim students who are subjected to harassment and death threats in a non-Muslim country, and is it permissible for us to treat the aggressors in kind?

A Muslim must not reside in a place where they are exposed to danger or the threat of death, because "Allah's earth is vast." If you are harmed, try to ignore it and repel it with kindness. Do not always reciprocate evil with evil, especially if you are a minority. It is wise to avoid friction with those who abuse you and to report them to the authorities for your protection. If that does not work, then move to another safe place for study, because self-abasement is not permissible in Islamic law.