1) Krakauer has a map that shows that there is a gauging station only half a mile downstream, which has a wire crossing the river, and a basket that one can ride across in. When they get to the station, they see that the basket is on the far side of the river, and it had been there when McCandless wanted to cross—had he known about it, he easily could have crossed to safety.
2) Krakauer uses his rock climbing hardware to pull himself across the wire. He then gets into the basket and heads back to the other side to ferry his companions across.
3) The bus is surrounded by lots of tiny bones from the small game that McCandless ate, as well as the skeleton of the moose that he so regretted killing.
4) Some people have compared McCandless to Sir John Franklin, a nineteenth century British naval officer. On the first trip he leads through the wilderness of northwestern Canada, eleven men end up dead from starvation, sickness, and murder, and all are only days from starving when they are rescued. Because he survives, he is promoted, but his lack of survival skills and his unwillingness to acquire any meant that when he chooses to go on another Arctic expedition, this time leading 128 men, not one of them is ever heard from again.
5) The contents of his journal is detailed in about 5 paragraphs right here on Gradesaver. Simply follow the link listed under resources.