Where does one acquire the viper venom.  I killed a bunch of snakes in the maze, but only got scales and fangs.  Is it just a low drop rate, or is there a particular type of snake that gives them?

The drop rate is low. You get good results if you exit the maze to the west (dead end area with loot) and re-enter the maze. There should be a snake close by (all enemies respawn if you leave a map) so use that to your advantage    to optimize farming results.