Varies: There is no specific dangerous heart rate during exercise. How fast your heart beats with exercise depends on a number of factors, especially your conditioning. If you are healthy, a heart reate in the 170's or even higher may be ok and tolerated.
Motion sickness caused by video games, sometimes called simulator sickness, is caused when there is a disconnect between what your eyes are seeing and what your body is feeling.
Even viewing a 3D movie may cause symptoms of motion sickness. Once a person gets used to the movement and the motion stops, symptoms may come back (although usually only briefly). Sometimes just thinking about movement can cause anxiety and symptoms of motion sickness. For example, a person who had motion sickness before might get nauseous on an airplane before take off.