Actually you make a great argument for what the actual guy went through. The movie was a bit hyped, but to tell you the truth Leanardo should have won an Oscar long before this movie ( in Gilbert Grape) he was incredible.
Wikipedia has the history of the actual life of the character. The movie strays from the actual events (Hollywood put a twist on it), but the history of what he went through to get to the Fort is amazing. Check it out when or if you can.