Ending too drawn out/unrealistic
It would have been better if he was already dead when reaching the unit in the forest. The night town being symbolic of a journey through hell and the song (which is about going to heaven) being an allusion to his death/afterlife. None of the finding the other brother or halting an attack was necessary.
The death could have occurred anywhere between his first gunfight to the rapids and waterfall. It is highly unlikely to survive rapids or falling over waterfalls in the first place.
Also annoyed how coincidentally the water somehow took him to exactly where he needed to be.