If a demo expects PAL, it's got to be played in PAL. There's more to NTSC/PAL than just the video display. A lot of hardware-banging programs rely on the subtle timing differences between them, too. That could also explain the crashing. I think you need an Amiga monitor or a scandoubler.
Other things to consider, what era demos are you trying to run? If they're especially old, they might be getting confused by the 030 and Kickstart 2.
