First, obviously set the difficulty to Master.
Now using the console use this command:
player.set 0
For each of the skills.
(Use speechcraft instead of speech when doing the speech skill.)

Then
player.setav Health 50
player.setav Magicka 50
player.setav Stamina 50

This should increase the difficulty greatly.

For other known console commands:
http://elderscrolls.wikia.com/wiki/Console_Commands_%28Skyrim%29
I don't know if they all work. I have tested the ones above however.
Enjoy.