Can I make it boot up as the last one listed on lilo?
Sure. Just post your /etc/lilo.conf here and someone will edit it.

Is there any way to turn it up?
Almost certainly. By default, just about all the mixers start with a low volume (so as not to deafen the unwary).

As a first step, go to

Kmenu>Multimedia>KMixer (a small icon will appear on your taskbar, usually bottom right). Right click on it and select Show mixer window and whack the volume up.