Audio skipping typically means you don't have enough power to handle running the sound. This is quite likely the case too with just 450MHz. You can lower the sound quality in the config file, up the prebuffer, try lowering the CPU cycles you're using, and upping the frame skip. Also, using Roland or General MIDI for the music is typically much more stable on OS X than adlib for me. All of these should be able to help somewhat, but you shouldn't get your hopes up too high either. On my Mac mini (1.42 GHz G4) I've got it running with smooth sound but I can't afford to up the cycles far enough to keep it running full speed compared to the SNES original mentioned bellow.
As an alternative I hope you realize this same game exists on the SNES and Snes9x tends to require less horsepower and tweaking on OS X.