Employment Law Questions? Ask an Employment Lawyer.
I am so sorry to read about your difficulties.
As you may know, your employer can terminate you or force you to resign for any reason or for no reason at all so long as the reason for this action is not on any one of the prohibited grounds of race, gender, age (40 and over), disability, national original or the like. Even if the reason is unfair as in this situation, the employer's action is still legal. Nevertheless, if your manager did not follow proper protocol in threatening to terminate your employment or demanding for your resignation, you may escalate your complaint to the employer's appeal process and ask for review of the manager's action.