G'Day Jon,
How's your collimation on that scope? I can see what you mean. The lines are there but instead of being a straight line across the spectrum, they appear curved, and the zero order image looks a bit of a mess. I'm thinking both are perhaps collimation related.
Assuming the collimation is right, you should be able to focus the zero order image to a nice round star, then adjust focus on the spectrum for minimum width. You should see the lines become more definite as well in the process.
It may take a bit of practice to get the focus right because there will be a difference in focus between the red and blue ends, so it's a compromise unless you are only interested in a specific line (say Ha) but that's probably unusual for a SA.
FYI Not all stars have lines that are visually distinct in an SA, but you should nearly always be able to pick the Telluric O2 band in the deep red end once you know what you're looking for.
Often you can't pick the lines until its binned in VSpec.
Al.