I think saving between levels is more or less how the game would have been done on a home console in modern times. The saving mid-level I did jsut because the last level is way tough for the time we have by then, and I wanted to see the ending. Even with those 3 saves, it was still quite hard (try it if you want).
My "genuine" score without states is about 50k, getting to the Ultimate level but not clearing it. I may try to improve this and finish without using states.
My first finish with states, 85k, my last scores with a new finish is 90k (also with states but only on the Aerial Race and on the Last level, after finding out I could get an extra 5k points in level 1
My best score without states is 55k, that is reaching last level but losing there.