I went to the screencast first, and the audio quality struck me as well. You're too close to the mic. Gotta back up (physically) and keep your record levels near the top of the green. As you speak, try to modulate your voice. If you're not recording in a studio, a simple trick is to put a blanket behind the mic. This will let you back up from the mic and raise your levels without catching reverb or background noise.