The dog does not technically die, though they make you believe it does at first. The dog is "shot." It is not shown on screen, but you can hear it. They show a quick glimpse of the bloody dog laying on the floor and he is whimpering so its hard to watch. However, later on in the movie, you find out that it was all just stage effects and the dog was not actually harmed.
Sort of. The premise involves someone voluntarily signing up for an extreme experience. Though they consent to enter it, simulated kidnapping/imprisonment is a major part of it.
Time in a mental institution is implied, and there are multiples scenes of the main character in therapy. Mental health, institutionalization, and suicide attempts are discussed/implied.