This appears to be a bug in Blender itself. It's reproducible manually:

1. Enable/disable auto keying
2. Undo the last action (using the undo history to really be sure)
3. Auto keying does not change

You are not. Delete it and download it again from http://steamreview.org/BlenderSourceTools/

Update the addon.

Turing it off during export is intentional, but it should be turned back on by Blender when the export completes. Which version of Blender are you using?

Blender 2.79 hasn't been supported for six years. You can download an older version of the Source Tools if you really want to use it: http://steamreview.org/BlenderSourceTools/archives/

This probably means a corrupt DMX in which the mesh uses more bones than it claims to.

You need to create Source materials yourself. Only material names are exported from Blender.

The button is only disabled if there is nothing in the scene to export. What does your Outliner look like?

I pushed a new commit which adds support for 8 bit and 64 bit integer values.

This doesn't affect model import/export so I won't create a new release of the tools.

Fixed in 3.3.2