When Tom loses his grip on the cliff and plunges into the river, the cliff face is actually gray fabric painted to look like rock. If you look carefully, it moves and bounces like fabric as he rolls down it.
Although Wade's revolver holds 6 cartridges, there are 7 shots: 1 shot at Maggie (the dog), 1 when Tom tries to get the gun from Terry (waking Wade), 2 more at Tom on the ledge, 1 when Wade shoots Ranger Johnny, 1 when Wade drops the gun into the water near the end, and Gail's final shot. Also, earlier Wade removes 3 spent cartridges, leaving 3 in the chamber, but when Gail opens it up, there's only 1 in the chamber.
After Tom jumps off cliff into the river he coaxes the family dog, a yellow lab named "Maggie", into jumping in after him. Throughout the entire movie the dog is called "Maggie" and referred to as "girl" but when the dog leaps from the cliff into the river, you can clearly see it's a male dog.
At 30:02 they are supposedly traveling alone through the wilderness. However you can clearly see in the background several people playing and fishing by the riverside with an aluminum rowboat up on the bank..
Throughout the movie, Gail warns the bad guys that there's no way out of the canyon other than via the Gauntlet, which only she can navigate. But Wade threatens to shoot her anyway. Moreover, Tom, the dad, runs ahead the boat and past the Gauntlet.