Hey guys,
Thanks a lot for your feedback.
My problem is partially solved now, anyhow. Since I wrote my original post here I lost my signal again and there was no way getting it back so I spoke with a friend that is a studio technician. I thought I had all in control as far as the settings in Focusrite's MixControl software goes, but my friend recommended me to reset to factory settings anyway and so I did thinking nothing will happen BUT suddenly I had a signal again. But it was still very very weak! My solution then was simply, as the same friend recommended, to switch to a balanced cable and I got the louder signal BUT now I have a noise-level issue that is impossible to work with. I have to crank my soundcards gain to almost maximum which must be what brings the noise so I ended up ordering a DI-box. I hope that will solve my noise issue.
Thanks for your kind help! Much appreciated.
I think there is nothing wrong with your SPDIF connection.
This is why I was asking what the maximum peak level of your DI-Signal is, when you hit the guitar.
The average level of the DI signal is quite low purposely, to allow for immense dynamic range, without compromizing the sound quality.