not sure about break/endquest. endquest seems more frequently used, but i have a quest that actually uses:
ACTN popup endquest break
i haven't had a problem w. the ENMY command; it might be the placement in the PAGE. here's mine for making the zorg hostile if you encounter them while carrying a certian item:
PAGE 0
REQ0 0
REQ1 1
ACTN popup endquest
MUSC music/vidcast.ogg
GFXP races/zorg.jpg 0
TITL Zorg Vidcast
TEXT blah
ENMY zorg
END PAGE
i have however had trouble making the garthan friendly if you deliver a certain item
my best suggestions are:
-base your quests off of similar ones that already exist/work. I can't always figure out why something that should logically work does not, but basing a quest off one that you know works gives you a head start.
-always attach some temp text describing what should be going on. i quickly found some quest were simply not firing when they should, or in the wrong order.