For the first problem, the alsa sound levels, I would do something like this in an init script:
if [ -f /etc/aumixrc ] ; then
ebegin "Loading Mixer settings"
/usr/bin/aumix -f /etc/aumixrc -L >/dev/null 2>&1
ebegin "Setting Mixer settings"
/usr/bin/aumix -v75 -c75 -w75 >/dev/null 2>&1
This will read mixer values from /etc/aumixrc and if it isn't there it'll just set the levels to 75%.
/usr/bin/aumix -f /etc/aumixrc -S >/dev/null 2>&1
Saves whatever your current settings are to /etc/aumixrc so when you boot up next time they will be the same.
As far as having the usb device mount automatically, you need to use supermount which I believe Mandrake includes automatically.