Maybe those guys saying that Aron should have had three or four knives on him could tell me this: which knife is best for cutting one's arm off?

I don't think field self amputation is something that people gear up for when they go out. (If you do and if you have personal experiences of using the gear, there is probably a whole publishing and movie industry that'd like to talk to you.) At the end of the day, he survived. He survived because he had the wit and the mental and physical fortitude to do what needed to be done. Sure, his equipment sucked, and it would have been better if he had been better equipped. But even with the best equipment (let's say those $500 knives), I'm not sure I can hack my arm off in the same situation.

The main lesson I've learned here is that I need to pack a bottle of Scotch.

Not to derail this thread, but I have read a lot on Theodore Roosevelt. His book "Through the Brazilian wilderness" is a fascinating read on the expedition down the "River of Doubt" (better known as the Amazon River.) The expedition members faced incredible hardships that makes modern day adventures, a walk in the park....

Also, Candice Millard's biographical book The River of Doubt is also a good read and also available as a Kindle download.