Can anxiety/stress cause someone to feel like a clenched fist is against the center of their chest and mimic heart attack symptoms?

Yes, somewhat typical with individual differences in reporting. A variety of other heart, lung and/or esophageal conditions other than a heart attack may behave in a similar ways and that is where workup is many times needed.

Yes. A diagnosis is not made from one symptom alone, especially when it concerns the heart. The risk factors, prior medical history, and findings on examination and the ECG are usually necessary before making a diagnosis of a heart attack.

Yes, There is specific name for this entity. You may visit this site for information on this topic: https://www.mayoclinic.org/diseases-conditions/broken-heart-syndrome/symptoms-causes/syc-20354617 Wish you good health!