Read all of the terminal command history in OS X

All of your history is stored in ~/.bash_history, where both reverse-i-search and the up/down keys use. That file is regularly pruned, but if you followed the guide in your link, the .bash_history file will practically never be pruned.

Personally, I would prefer to do it in a simpler way and print everything, instead of checking the latest session which doesn't cover all Terminal windows and all commands.

Get a full history

cd ~/.bash_sessions
cat *.historynew *.history

If you want to sort by session date

cd ~/.bash_sessions
cat `ls -tr *.historynew *.history`