I did all your suggestions once before.
The mixer shows 5 sliders (master, pcm, digital, ext mic, int mic) so no Capture.
Alsamixer in terminal shows Digital, ext mic, int mic all three at 100<>100.
'Sound Devices' in Skype shows default, 4 options of HDA Nvidia and hdmi, but no webcam.
I tried them all without succes. In the tutorial I see sliders I don't have in mixer (capture), so I think the problem is in alsamixer ?