No one can "force" you to sign anything or hold you hostage, but they can make you feel extremely uncomfortable and intimidated. You can excuse yourself and let them know you will respond to them by the end of the day (what are they going to do, fire you?).
As for being let go for being copied on emails that contain "non Med reg" topics and not reporting the sender - very low and clearly looking for reasons to get rid of people, but well within the company's rights. If you are aware of ethics violations and "look the other way", then the company can dismiss you. Is this always enforced? Of course not. But when they want to get rid of you AbbVie will do whatever is in their "power".
These topics lead full circle to the conversation around filing complaints with the OEC in the first place: if you work for an organization that is unethical, commits fraud and has a culture of "I don't care how you do it, but increase sales and MS"- understand one day the buck may stop at you even if you've been loyal and given years of service. Why would a company who's values clearly include "sales at all costs" then have a conscience shift and decide to "do the right thing and save those who have been loyal"?