I'm totally lost as to what your question is.

Obviously...(and I've never used Cakewalk before) but there must be some kind of preset to allow you to distinguish between a line input and a Mic input.

Sorry I can't be of more help but even my own equipment stumps me sometimes. I use an M-Audio 410 and plug the mic into the front input and the stereo output from the mixer into the back. I'm constantly forgetting to push the button on the front panel to tell the unit to allow the stereo guitar input instead of the mic input so I definitely feel your pain.

You have no idea how many times I've tried to start recording a lesson and getting no mic input only to discover that I have the stupid button pushed in for the rear inputs.

It's almost like a learning process of hit and miss. You have to screw around for weeks at a time before you realize that the company has designed the thing so stupidly that it's almost impossible to figure out.

And the .pdf manuals arre of no help whatsoever because they've been badly translated from Chinese or whatever.

About the only advise I can give is keep plugging and unpluging things until the thing works and then don't touch it again. (at least that's been my philosophy over the years :)