this is a hard one to think about long distance
once you hit record in ardour you are playing through the output levels in ardour that go through jack and then through your alsa mixer and you know you can output the track directly or have it go through the master so then in ardour you have two volume sliders working together.
as for the capture sound being distorted
if you can hear the guitar some capture device must be enabled yes ? like mix or something
(i'm not a guitar player)
but try only enable the mic capture (might need the capture capture)
there is a mic boost +20 becibells to turn on or off
*the mysterious controlls for alsa emu10k1 make me feel lke a retard ?*
anyway i think you have it correct when it sounds good
and if you can hear it capture is on has been my experience
i think also whatever mixer you are using most likely is not showing you what the possibilities are
try QAMix by Nathias Nagorni
it's a suse specific thing so you have to edit the paths in the Makefile (not hard) to get it to compile but it comes with a sample configuration for emu10k1 i like alot.
and of course look at the strange output of amixer and read man amixer